Windows Phone 7 Development

Localization in Mango

2011-11-25T10:05:00.001-08:00

Hi everyone! In this blog post, we are going to cover how you can create localized applications on Mango!

Today, a developer creates an application wich is used globally by people speaking and understanding different languages. It is always better if your application is localized to different regions. In this post, we will learn how to create such application and test the localization on emulator.

The application we are going to create will be very simple one but you can use the concept and code shared here to create whatever you intend to do. This sample application when seen in United States region will show text as "Hello Friends!" and when seen in Spain region, will have text as "Halo Amigos!" -

Steps to create Localized application

1. On the Solution File, Create a new Folder named "Localization" and add two resx files - "Strings.resx" and "Strings.es-ES.resx".

2. In String.resx, add an entry with name of string as "Localization.HelloText" and value as "Hello Friends!" -

3. In Strings.es-ES.resx, add an entry with name of string as "Localization.HelloText" and value as "Hola Amigos!"

4. As the default resource file is named "Strings.resx", the Neutral Language should be kept as "United States (English) under Projects -> Application Tab -> Advanced Assembly Information.

5. If you want to make this application support Spanish region, then open the .csproj file in text editor, add the following -

<SupportedCultures>es-ES;</SupportedCultures>

Add any number of cultures as you want your application to support!

6. Code needed to read the localized strings from resource file is as follows -

ResourceManagerresourceManager = new ResourceManager("Localization.Localization.Strings", Assembly.GetExecutingAssembly());

textBlock1.Text = resourceManager.GetString("Localization.HelloText", CultureInfo.CurrentCulture);

Note - CultureInfo needs "System.Globalization" while Assembly class needs "System.Reflection" and ResourceManager needs "System.Resources".

Steps to test the application on emulator

The following are steps to test the localization on emulator -

1. Go to Settings

2. Select Region + Language under Settings

3. For "Region Format" choose Spanish - Spain (es - ES)

4. Click on link for restarting the emulator to save the changes

5. Click on "Localization" application to start the application with region as Spain

And here you go!! The application is localized. Check out this applicaiton by changing the region back to United States. The text will be shown in English.

Encryption in Mango! Part II

2011-11-16T06:59:00.001-08:00

In this blog post, we will be creating a simple application in which the following things will happen -

1. The end user can enter a text in a text box which needs to be encrypted.
2. The applicaiton will store the encrypted text in the isolated storage and also show the encrypted bytes in string format to the end user.
3. The end user can choose to view the decrypted text back from the file stored in Isolated storage.
4. The application will read the encrypted bytes from isolated storage, decrypt the contents and show the decrypted text to the end user.

The following is how the application behaves -

The user can choose to enter any text in the first text box under label "Decrypted Text" and then choose the "encrypt" menu item to encypt the contents and store it in Isolated Storage -

On clicing "encrypt" applicaiton bar menu item, the "Hello World!" text will be encrypted and stored in Isolated Storage. The string representation of encrypted bytes stored in Isolated Storage would be shown in Encrypted text text box -

Now the user can choose to see the decrypted text back by selecting the "decrypt" menu bar -

How did we accomplish this programatically?

This example uses multiple things -
1. Usage of application bar
2. Usage of DPAPI and System.Cryptography classes and methods
3. Usage of System.IO and System.IO.IsolatedStorage

If you are not clear on Isolated Storage and Application Bar concepts, i would suggest you to look into my earlier blog posts on these topics.

Code -

Lets first look at the code which encrypts the contents and save contents to the Isolated Storage file -

private void Encrypt_Click(object sender, EventArgs args) {
string encryptedText = String.Empty;
string decryptedText = decryptedTextBox.Text;
byte[] encryptedBytes = null;
if (!String.IsNullOrEmpty(decryptedText)) {
// Convert the string to byte array as ProtectedData.Protect method expects a byte array.
byte[] decryptedBytes = System.Text.Encoding.UTF8.GetBytes(decryptedText);
try {
// Passing the decrypted bytes and setting the optional entropy as null.
encryptedBytes =
ProtectedData.Protect(decryptedBytes, null);
}catch (ArgumentNullException) {
MessageBox.Show("The text to be encrypted can't be empty");
}catch (CryptographicException cryptException) {
MessageBox.Show("Crypt failed , Error Message : " + cryptException.Message);
}

catch (NotSupportedException notSupportedException) {
MessageBox.Show("OS platform does not support this method. Check with the distributor if you have the right version of Windows Phone , Error Message : " + notSupportedException.Message);
}
catch (OutOfMemoryException) {
MessageBox.Show("OOPS! There is not enough memory on the device to execute this operation.");
}
// Saving the encrypted bytes to Isolated Storage
if (encryptedBytes != null) {
using (IsolatedStorageFile isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication()) {
using (IsolatedStorageFileStream fileStream = new IsolatedStorageFileStream("Hello.txt", System.IO.FileMode.OpenOrCreate, isolatedStorageFile)) {
BinaryWriter binaryWriter = new BinaryWriter(fileStream);
binaryWriter.Write(encryptedBytes);
binaryWriter.Flush();
binaryWriter.Close();
}
}
encryptedText = System.Text.Encoding.UTF8.GetString(encryptedBytes, 0, encryptedBytes.Length);
}
}// Showing the string representation of the encrypted bytes on the screen.
this.decryptedTextBox.Text = String.Empty;
this.encryptedTextBox.Text = encryptedText;
}

In the code above, we are doing the following -
1. First we are retrieving the text from text box and checking if the decrypted text is empty or not.
2. If the decrypted text is not empty or null, then we convert the string to byte array.
3. We use ProtectedData.Protect method whose input is the byte array. We set the optional entropy as NULL. Note - The developers can set entropy to strengthen the key and add one more layer of security.
4. After the bytes have been encrypted, we save them to Isolated Storage using IsolatedStorageFile, IsolatedStorageFileStream and BinaryWriter classes.
Note - If you are writing the string, use Stream Writer. For writing bytes, it is recommended to use BinaryWriter.
5. We are showing the string representation of encrypted bytes on the text box.

Now the code for decryption of the code -

private void Decrypt_Click(object sender, EventArgs args) {

string encryptedText = encryptedTextBox.Text;
string decryptedText = String.Empty;
byte[] encryptedBytes = null;
if (!String.IsNullOrEmpty(encryptedText)) {
//Retrieve the encrypted bytes from the Isolated Storage of phone.
byte[] decryptedBytes = null;
try {
using (IsolatedStorageFile isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication()) {
using (IsolatedStorageFileStream fileStream = new IsolatedStorageFileStream("Hello.txt", System.IO.FileMode.Open, isolatedStorageFile)) {

BinaryReader binaryReader = new BinaryReader(fileStream);
encryptedBytes = binaryReader.ReadBytes(Convert.ToInt32(fileStream.Length));

}
}// Decrypt the encrypted bytes by using Unprotect method of ProtectedData class of System.Security.Cryptography.
decryptedBytes = ProtectedData.Unprotect(encryptedBytes, null);
}
catch (ArgumentNullException) {
MessageBox.Show("The text to be decrypted can't be empty");
}catch (CryptographicException cryptException) {
MessageBox.Show("Crypt failed , Error Message : " + cryptException.Message);
}catch (NotSupportedException notSupportedException) {
MessageBox.Show("OS platform does not support this method. Check with the distributor if you have the right version of Windows Phone , Error Message : " + notSupportedException.Message);
}catch (OutOfMemoryException) {
MessageBox.Show("OOPS! There is not enough memory on the device to execute this operation.");
}               // Convert the decrypted bytes to its string representation
if (decryptedBytes != null) {
decryptedText = System.Text.Encoding.UTF8.GetString(decryptedBytes, 0, decryptedBytes.Length);

}
}
// Showing the decrypted text on the text boxes
this.decryptedTextBox.Text = decryptedText;
this.encryptedTextBox.Text = String.Empty;
}

In the code above, we are doing the following -
1. First we are retrieving the encrypted bytes from Isolated Storage using IsolatedStorageFile, IsolatedStorageFileStream and BinaryReader classes.
2. We use ProtectedData.Unprotect method whose input is the byte array. We set the optional entropy as NULL. Note - The developers can set entropy to strengthen the key and add one more layer of security.
4. After the bytes have been decrypted, we convert them to string representation and show the decrypted sting in the text box.

In my next blog, i will be using this strategy to save complex data types and also will share some tips to use optional entropy field.

Encryption in Mango!

2011-11-09T19:26:00.001-08:00

In this blog post, we are going to cover how the developers can now save data in encrypted format in Windows Phone.

In Mango, the Windows Phone team has provided the developers with DPAPI (Data protection API) and methods - Protect and Unprotect which can be used to encrypt and decrypt the data.

Why should i be excited about this?
Until now, there was no secure way of encrypting your data due to which developers were not able to enable the offline scenarios in line of business and enterprise applications. Ofcourse, if you are developing a game or a fun application and not storing any PII information, you could simply save the data in plain text to either Isolated Storage or the Transient Storage.

So, for the mobile developers who are developing enterprise applications and even for those who were eagerly waiting for Windows Phone to have a proper secure encryption standard, IT IS A BIG DEAL!

What is DPAPI?
I will not be covering the concept of DPAPI in detail. There are lots of blogs and articles on this technology which you can read to get the grasp of the concept -

http://msdn.microsoft.com/en-us/library/ms995355
http://blogs.msdn.com/b/shawnfa/archive/2004/05/05/126825.aspx

"In context of Windows Systems, DPAPI works by generating a key from the current user's credentials and then generates a master key. DPAPI then encrypts the master key with the key generated from user's credentials. Then a random session key is created for each call to the CryptProtectData method. This session key is generated from the master key, some random data, and some optional entropy passed in by the user to strengthen the key. This session key is used to do the actual encryption!"

DPAPI in MANGO

Before DPAPI was introduced, there were other ways possible to encrypt your data using AES APIs but the issue was how to secure the key used to encrypt and decrypt the data. Saving the key on the phone was not recommended approach. The only possible and tedious way was to store the key on a server side and then get the key from server via a web service which then needed to be claims - aware (as this is the only way any enterprise application can interact with a web service). So overall, the encryption and decryption was neither developer-friendly nor recommended by the experts!

DPAPI solves the problem of generating and handling the keys used to encrypt the data in a secure manner. As mentioned earlier, it will generate the key on the basis of user and phone credentials. On a windows phone device, every application gets its own decryption key, which is created when the user runs the application for the first time. The methods provided by the Cryptography API - Protect and UnProtect will use this key implicitly. The key will also persist across updates to the application.

Enough theory!! Tell me the API
Fair thought! I myself am not a big fan of theory but it helps to understand the concepts.

The two methods that you would be using are - Protect and Unprotect.
These methods are present in System.Security.Cryptography in mscorlib.Extensions.dll.

I will be writing the second part of this blog which will have a running sample of Encryption and Decryption using DPAPI.

OData and Windows Phone - Using Entity Framework Code First - Part III

2011-11-09T19:25:00.005-08:00

Expect an update by 24th November 2011. Completed the Encryption blog first :)

OData and Windows Phone - Part I

2011-11-09T19:25:00.001-08:00

Hi Folks! This blog will cover aspects of creation of OData service in WCF (they are known as WCF Data Services) and how to consume them on Windows Phone Device.

What is OData?
OData (Open Data Protocol) is a web protocol to perform querying and updating data. The protocol allows a consumer ( clients built on .Net, Java, PHP, JavaScript, Mobile devices like Windows Phone, iPhone etc.) to query a database over the HTTP protocol and get back the result in different formats like XML,JSON or ATOM, including pagination, ordering or filtering of the data.

WCF Data Services
WCF Data Services (previously known as ADO.Net Data Services) provides developers with client libraries for .Net, Silverlight, AJAX, PHP and Java. Microsoft is supporting OData in SQL Server 2008 R2, Windows Azure Storage, Excel 2010 (through PowerPivot) and SharePoint 2010.
WCF Data Services support both relational data (via Entity Framework 4.0 models and 4.1 Code First Frameworks) and non-relational data-sources which can be exposed as EDM and exposed as a data service.

Exposing data using WCF Data Service
Let us take a simple example -
1. We will create a small table lets say Organization in SQL Server.
2. We will expose this table using Entity Framework Models.
3. We will expose the entities of Entity Framework Models via WCF Data Services.
4. Make changes on Windows Phone Client side to invoke and retrieve data from WCF Data Services.

I have created a table named organization in SQL Server in ./SQLExpress -

create table Organization

(OrganizationID
int PRIMARY KEY identity(1,1),

OrganizationName varchar(255),

CountryName varchar(200)

)

It has three records as of now -

Now, we will create a WCF Data Services Project in VS 2010 -

As seen in the diagram, the data service name is WcfDataService1.svc

Now, we will add an entity framework model (edmx) in this project. Right click on the project --> Click on Add --> New Item. Choose "ADO.Net Entity Model" from Data templates.

You will get an option whether to create a model from scratch or create from database. In this blog post, we will go ahead with creating an entity model from the database directly.

Click Next and then set the connection strings to the appropriate server and database so that the wizard can access the table and create entity model corresponding to that -

Choose the table "Organization" from the list of database objects -

Click "Finish" button to add the entity model to the project.

Now in order to expose this entity model as OData service, you need to make the following changes in WcfDataService1.svc.cs -

1. Inherit the WcfDataService1 with DataService<T> where T represents data sourcepublic class WcfDataService1 : DataService<LoggingEntities>

2. Make changes to the InitializeService method -

public static void InitializeService(DataServiceConfiguration config)

{

config.SetEntitySetAccessRule("Organizations", EntitySetRights.AllRead);

config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;

}

As seen in the method, the entity "Organizations" is being exposed with rights as Read.

Run the project by pressing F5, the Url - http://localhost:47836/WcfDataService1.svc/ will be -

<?xml version="1.0" encoding="UTF-8" standalone="true"?>
<service xmlns="http://www.w3.org/2007/app" xmlns:app="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" xml:base="http://localhost:47836/WcfDataService1.svc/"> -<workspace> <atom:title>Default</atom:title> -<collection href="Organizations"> <atom:title>Organizations</atom:title> </collection> </workspace> </service>

If you try reading the data with respect to Organizations, type in the following on the browser -

http://localhost:47836/WcfDataService1.svc/Organizations/

The following will be output of this (list of all organizations) -

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>

<title type="text">Organizations</title>

<id>http://localhost:47836/WcfDataService1.svc/Organizations/</id>

<entry>

<id>http://localhost:47836/WcfDataService1.svc/Organizations(1)</id>

</author>

<m:properties>

<d:OrganizationID m:type="Edm.Int32">1</d:OrganizationID>

<d:OrganizationName>Data Logistics</d:OrganizationName>

<d:CountryName>Germany</d:CountryName>

</m:properties>

</content>

</entry>

<entry>

<id>http://localhost:47836/WcfDataService1.svc/Organizations(2)</id>

</author>

<m:properties>

<d:OrganizationID m:type="Edm.Int32">2</d:OrganizationID>

<d:OrganizationName>Karan Corp.</d:OrganizationName>

<d:CountryName>India</d:CountryName>

</m:properties>

</content>

</entry>

<entry>

<id>http://localhost:47836/WcfDataService1.svc/Organizations(3)</id>

</author>

<m:properties>

<d:OrganizationID m:type="Edm.Int32">3</d:OrganizationID>

<d:OrganizationName>United Corp.</d:OrganizationName>

<d:CountryName>United States</d:CountryName>

</m:properties>

</content>

</entry>

</feed>

In the next part of this blog, i will integrate this OData service with Windows Phone applications.

Launchers and Choosers in Mango Unleashed - Part III - Email, SMS, Contacts and Call

2011-11-09T19:24:00.001-08:00

Hello everyone! In this blog post, we will explore the different APIs provided in Mango related to Email, SMS and Phone Call (3 primary ways you want to communicate with folks in addition to the other social networking sites).

Mango provides you different APIs related to Email, SMS and Phone Call in form of "Lanchers and Choosers" :

1. Task(s) related to SMS - As of today, there is a single launcher available named "SmsComposeTask" which is used to send an SMS to a contact. The properties and methods of SmsComposeTask are -
1. Body - Body of the text message to be sent to the recipient
2. To - Recipient Name as present in the phone
3. Show() - This method will launch the Messaging task.

For example -
SmsComposeTask smsComposeTask = new SmsComposeTask();
smsComposeTask.To = "Karan Vohra";smsComposeTask.Body ="Hi..Wassup!";
smsComposeTask.Show();

With the above values, the "To" and "Body" attributes of SMS will be pre-populated as follows -

Note - On emulator, if you try sending the SMS, the message will not be sent to the contact. Also, when the SMS Compose Task is launched, the current running application is de-activated, so make sure that you save the data in either transient and permanent storage.

2. Task(s) related to Phone Call -

There are three major Launcher and Choosers available related to Phone Calls -
a. PhoneCallTask - This launcher can be used to call a phone number.
b. SavePhoneNumberTask - This chooser can be used to save a phone number along with a display name.
c. PhoneNumberChooserTask - This can be used along with Phone Call Task to choose and call a contact.

Let us use Phone Call Task and Phone Number Choose Task with following application -

We will create a simple application which will allow the end user to choose a phone number from list of stored contacts and upon selecting the contact, call will be made to him/her.

On Page_Load of this application, Phone Number Choose Task is called in the following manner -

PhoneNumberChooserTasknumberChooseTask = new PhoneNumberChooserTask();

numberChooseTask.Completed += new EventHandler<PhoneNumberResult>(numberChooseTask_Completed);

numberChooseTask.Show();

Upon selecting a contact, we need to make call to that contact. This can be accomplished using the following piece of code -

void numberChooseTask_Completed(object sender, PhoneNumberResult e) {
string phoneNumber = String.Empty;
string displayName = String.Empty;
PhoneCallTask phoneCallTask = null;
if (e.Error != null) {
Exception exception = e.Error;

Dispatcher.BeginInvoke(() => { MessageBox.Show(exception.Message); });
}else {
if (e.TaskResult == TaskResult.OK) {
phoneNumber = e.PhoneNumber;
displayName = e.DisplayName;
phoneCallTask = new PhoneCallTask();
phoneCallTask.DisplayName = displayName;
phoneCallTask.PhoneNumber = phoneNumber;
phoneCallTask.Show();
}

}

}

Before completing this topic, let us also cover how SavePhoneNumberTask works. It is as simple as the following 4 lines of code -

SavePhoneNumberTask savePhoneNumberTask = new SavePhoneNumberTask();

savePhoneNumberTask.PhoneNumber = "999999999";

savePhoneNumberTask.Completed += new EventHandler<TaskEventArgs>(savePhoneNumberTask_Completed);

savePhoneNumberTask.Show();

On running this peice of code on emulator and on phone, following happens in sequence -

3. Task(s) related to Email - There are two tasks related to Email - One to choose the email addresses from contacts stored in phone and the other to save the email address to phone -
SaveEmailAddressTask and EmailAddressChooserTask.

The only properties for SaveEmailAddressTask are - Email Address (string) and Display Name (string).

The properties that can be retrieved from EmailAddressChooserTask in Completed event are EmailAddress and DisplayName.

The usage of these are same of as of the phone tasks and SMS tasks!!

Launchers and Choosers in Mango Unleashed - Part II - Integrating with Social Networks

2011-10-29T10:04:00.000-07:00

Hi Folks,

In this blog, we will cover two new interesting launchers which will help you in integrating your applications with the Social Networks like Facebook and Windows Live Messenger. In coming days, the same API might be used to integrate with Twitter and other social networking sites.

The two new launchers introduced in Mango are -
1. ShareStatusTask
2. ShareLinkTask

As their names denote, the ShareStatusTask helps you to share the status on Social Networks like Facebook and Windows Live Messenger. With help of ShareLinkTask, you can share the Web URL with the friends directly from you Windows Phone application!!

Note - These two launchers won't work on Emualtors. They can work if your Windows Phone is developer unlocked and you try running the code directly on the device by attaching it to computer (via USB) and then choosing "Windows Phone Device" as deployment target in Visual Studio IDE.

The following are the code samples to use these in your applications -

ShareLinkTask shareLinkTask = new ShareLinkTask();

shareLinkTask.Title = "Awesome music";

shareLinkTask.Message = "Listen to this folks!";

shareLinkTask.LinkUri = new Uri("http://www.youtube.com");

shareLinkTask.Show();

ShareStatusTask task = new ShareStatusTask();

task.Status ="I am developing on Mango!";

task.Show();
When you call the Show method, a screen will open where you will be asked to confirm the status message and social network you want to post the message. This is to avoid misuse of this feature.

Cheers!

New Launchers and Choosers in Mango Unleashed Part I- Bing Maps Integration

2011-10-28T12:00:00.000-07:00

Folks,
In this blog, we are going to discuss new launchers available in Mango - Bing Map Integrations!! The two launchers available in Mango are -
1. BingMapDirectionsTask - This task takes two parameters- Start and End locations and will give you directions on Bing Map to navigate from Start to End Location.
2. BingMapTask - This task will pin point the location or Search term on the Bing map.

What has changed?
Earlier to implement the Bing Map API functionality, the developers used to get a key and use web Service APIs to build routes on maps and pin-point locations on maps which required a lot of effort and learning.

With these two launchers and maximum of 3-4 lines of code, you can implement this functionality fairly easily.

Implementation

BingMapTasks
The important properties of this launcher are -
1. Center - It if of type GeoCo-ordinate. If this is not set, then the user's current location will become the center. This location is used as center point for the map.
2. SearchTerm - This is a string and it is used to search and tag locations on the map. It can be the name of the place, type of place or anything else.
3. ZoomLevel - This gets the initial zoomlevel of the map.

Code for BingMapTasks -

BingMapsTaskbingMapTask = new BingMapsTask();

bingMapTask.ZoomLevel = 1.0;

bingMapTask.SearchTerm ="Chandigarh,India";

bingMapTask.Show();

BingMapDirectionsTask

This launcher will give you directions to reach from a Start to End Location. It has two properties-
1. Start - LabeledMapLocation which can be determined either with a label (like "Patiala,India) or a Geo-cordinate
2. End - Same as Start.

The following is the code to implement this launcher -
BingMapsDirectionsTask directionsTask = new BingMapsDirectionsTask();

LabeledMapLocation startLocation = new LabeledMapLocation();

startLocation.Label ="Patiala,India";

LabeledMapLocation endLocation = new LabeledMapLocation();

endLocation.Label = "Chandigarh,India";

directionsTask.Start = startLocation;

directionsTask.End = endLocation;

directionsTask.Show();

If you want the Geo-coordinates of location, you can use the emulator to find that out in the following manner -

On the windows phone emulator press the ">>" option available on top right hand side. A window will open, click on Location tab and then enter the location for which you need to retrieve Latitude and Longitude -

Using the latitude and longitude, you can create the instance of GeoLocation. (You need to add reference of System.Device.dll)

System.Device.Location.GeoCoordinate coordinate = new System.Device.Location.GeoCoordinate(30.3280, 076.3849);

Creating Application Bar programmatically on Mango

2011-10-28T10:25:00.000-07:00

Folks,
This blog will cover how you can create an Application Bar dynamically (programmatically) on Mango platform!

Basic properties of Application Bar -
1. Foreground Color - Color of font and icons used
2. Background Color - Background color of the application bar
3. Opacity - It can be either 0,0.5 or 1.0
4. IsVisible - Either make the application bar visible or invisible
5. IsMenuEnabled - If it is enabled, then then end user will see the application bar menu items or not.
6. Mode - This is either default (in which the icons are shown to the end user along with ellipsis which mazimize the application bar) or Minimized (in which the icons will be hidden and only ellipsis will be shown to the end user)

In addition to above, application bar menu items and application bar icon buttons can be added to the Application Bar by using Menu Items and Buttons properties respectively.

How to programmatically add Application Bar on your Mango Application Page?

You need to get the ApplicationBar instance of the page and set its properties in the following manner -

this.ApplicationBar = new ApplicationBar();

this.ApplicationBar.IsVisible = true;

this.ApplicationBar.Opacity = 1;

this.ApplicationBar.Mode = ApplicationBarMode.Minimized;

The above piece of code creates an application bar which is visible, has opacity of 1 and is in minimized mode.

How to create an Application Bar which is Theme Aware?
I have been asked questions on how to create an application bar which has application bar icon buttons which change their color when the background changes from Light to Dark.

Here is how you can do this- Create a ResourceThemeLocator class which identifies whether the theme selected is Light or Dark and chooses the appropriate Icon Button Image. Then use the class's properties to get the URI of the icon image and use it while constructing the application bar dynamically.

namespace LaunchersAndChoosers {
public class ThemedResourceLocator {

private readonly Wp7Theme theme;

public ThemedResourceLocator() {
var resource = Application.Current.Resources["PhoneForegroundColor"];
if (resource != null) {
this.theme = (Color)resource == Color.FromArgb(222, 0, 0, 0) ? Wp7Theme.Light : Wp7Theme.Dark;
}
else {
this.theme = Wp7Theme.Dark;
}
}
       public enum Wp7Theme {
Dark,
Light
} public string SearchIcon {
get {
return GetImagePath("appbar.feature.search.rest.png");
}
}       private string GetImagePath(string fileName) {
var folder = this.theme == Wp7Theme.Dark ? "Images/dark/" : "Images/light/";
return Path.Combine(folder, fileName);
}
}
}
The code is pretty simple - In the constructor of the class, we are retrieving what is Foreground Color - either light (White) or Dark (black) and on the basis of that we are setting theme property which can either be Light or Dark.
SearchIcon is the image we plan to use on the Application bar. If the theme is light (white), the image URI picked will be in location - Images\light and if the theme is dark (black), the image URI picked will be from location - \Image\dark folder.

Note - The name of the imge in both light abd dark folder should be the same. Also remember to set the Build action of images to be used on the Application Bar as Content.

The following code describes how we dynamically create an application bar, add an application bar icon button to it, set the image of the icon button on the basis of the theme and also hook up the click event of the application bar icon button to a callback method.
public partial class MainPage : PhoneApplicationPage {

// Constructor
public MainPage() {
InitializeComponent();
}private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e) {
}
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e) {
ThemedResourceLocator themeIdentifier = new ThemedResourceLocator();
this.ApplicationBar = new ApplicationBar();
this.ApplicationBar.IsVisible = true;
this.ApplicationBar.Opacity = 1;
this.ApplicationBar.Mode = ApplicationBarMode.Minimized;
ApplicationBarIconButton chooseAddressIconButton = new ApplicationBarIconButton(new Uri( themeIdentifier.SearchIcon , UriKind.RelativeOrAbsolute));
chooseAddressIconButton.Click +=
new EventHandler(chooseAddressIconButton_Click);
chooseAddressIconButton.Text ="Choose";
if (this.ApplicationBar != null) {
this.ApplicationBar.Buttons.Add(chooseAddressIconButton);
}
base.OnNavigatedTo(e);
}

void chooseAddressIconButton_Click(object sender, EventArgs e) {
AddressChooserTask addressChooserTask = new AddressChooserTask();
addressChooserTask.Completed +=
new EventHandler<AddressResult>(addressChooserTask_Completed);
addressChooserTask.Show();
}
void addressChooserTask_Completed(object sender, AddressResult e) {
AddressResult res = e as AddressResult;
if (res.TaskResult == TaskResult.OK) {
MessageBox.Show("Display Name : " + res.DisplayName + ", Address Name : " + res.Address);

}} }

In the above code, we have done the following -
1. In the OnNaviagtedTo event, we have initialized an Application Bar , set its properties, added Application Bar Icon Button to the Application Bar and also set the Click event of the Icon Button.
2. On click of button, the "ChooseAddressTask" launcher is shown to the end user where the end user can select any of the saved contacts present in the device.
3. If the user successfully chooses the address,the display name of the contact and address will be displayed in a message Box to end user.

MANGO!!

2011-10-26T11:48:00.001-07:00

Going through the features exposed by Mango and totally excited about them!!

Stay tuned for some exciting tutorials and blogs on what's new in MANGO for the developers!!

Using timers in Windows Phone 7 Applications

2011-10-26T09:09:00.000-07:00

Some of the folks that i interacted with recently asked me how to have functionality in windows phone applications which will repeat after a particular period of time.

The answer is pretty simple - We can use "Timers" concept in Windows Phone Applications. System.Threading has Timer class which can be used to create periodically repeating tasks!

In this post, i will create a very simple application in which the end user will be intimated with the Current Date Time in form of message box after every 5 seconds. We will use the Timer class to accomplish this!

Step 1 -

In the Page Load event of the page, add the following line of code -

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e) {

Timer timer = new Timer(this.TellTime, null, 1000, 5000);

}

We have simply created an instance of type System.Threading.Timer class and it has 4 parameters -
1. TimerCallback delegate - This points to the method which will be called after periodic intervals. Whatever logic or business rule you want to execute after periodic interval should be kept in this method.
2. State - It is of type System.Object and it is the input parameter pointed by TimerCallback delegate.
3. DueTime - It is in milliseconds and it is the duration after which the first invocation of callback takes place.
4.Period - It is in milliseconds and this is the amout of time to delay before the callback is invoked.

So, the above piece of code means that the method "TellTime" will be called after an initial delay of 1 second and will be periodically called after 5 seconds. We are passing no parameter to TellTime method.

Add the method TellTime to the class -

public void TellTime(object stateInfo) {

Dispatcher.BeginInvoke( () => MessageBox.Show("Date Time is :" + DateTime.Now.Hour.ToString() + ":" + DateTime.Now.Minute.ToString() + ":" + DateTime.Now.Second.ToString() + "." + DateTime.Now.Millisecond.ToString()));

}
As shown in the above piece of code, a message box will be shown to the end user displaying the current date and time after every 5 seconds.

But how will you stop the timer once the task is finished - You need to somehow set a flag that will determine whether the timer should run or stop. For accomplishing this task, use "AutoResetEvent" class in the following manner -

namespace TimersUsage {

public partial class MainPage : PhoneApplicationPage {

private int count;

AutoResetEvent autoEvent;

// Constructor

public MainPage() {

InitializeComponent();

count = 0;

}

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e) {

autoEvent = new AutoResetEvent(false);

Timer timer = new Timer(this.TellTime, autoEvent,1000,5000);

autoEvent.WaitOne();

MessageBox.Show("End of timer, signal has been set");

timer.Dispose();

}

public void TellTime(object stateInfo) {

AutoResetEvent autoEvent = (AutoResetEvent)stateInfo;

count++;

if (count >= 2) {

autoEvent.Set();

}

}

}

}

As shown in the code, after the code in TellTime method is run for 2 times, the flag will be set via autoEvent.Set method.
The autoEvent.WaitOne() method will stop the current thread execution until the flag is set via autoEvent.Set method. Once the flag is set, a message box will be shown to the end user , the timer object will be disposed and the code within TellTime method will not be called.

Background workers in Windows Phone Applications

2011-10-23T11:53:00.000-07:00

This post describes how to perform operations in the background in a Windows Phone Application using "Background Workers"

I will explain this concept using a very simple example of calling a web service on a separate thread using background worker.

Why do we use separate threads? To improve the performance of your application, to have a separate thread do the heavy-lifting for your primary UI thread, to perform an operation on the background without freezing the current UI, to implement fire and forget patterns in your applications etc.

In my previous post, i called a web service's method to get the top 10 movies of all times. In this post, i will use the back-ground workers to make the call to the web service. Until, the application does not get the response, we will show a Loading message and once the result comes from the web service, we will display the Top 10 movies of all times and loading message will be hidden.

The back ground workers have 3-4 simple methods & events -

1. DoWork - The method subscribed in this event is called whenever the WorkAsync() method of the back ground worker is called. The method subscribed will run in a thread different from the parent UI thread.

2. RunWorkerCompleted - The method subscribed in this event is called whenever the execution of method called in DoWork event is completed. In other words, the method subscribed in this event is called once the execution of the background worker completes.

3. RunWorkerAsync() - When this method is called, it marks the invocation of the background worker's DoWork() event. This method is generally called once you have set both the DoWork and WorkCompleted events.

In addition to the above methods and events, there are certain other events like ProgressChanged event, ReportProgress method to send continous feedback to the parent thread on the progress of execution in the back-ground thread.

The solution is - We will add a button and a label (for loading text) on the UI. ON the click of the button, we will invoke the background worker. The back ground worker will invoke the web service. From the time of invocation of web service till the result is displayed on screen, we will show a loading message on the screen.

The following is the piece of code you need to introduce to make it work - :)

#region Private Variables
private BackgroundWorker backgroundWorker;

#endregion
// Constructor
public MainPage() {

InitializeComponent();

textBlock1.Visibility = Visibility.Collapsed;

}

void client_GetTop10Completed(object sender, GetTop10CompletedEventArgs e) {

www.kirupafx.com.ArrayOfString resultSet = e.Result;

listBox1.ItemsSource = resultSet;

Dispatcher.BeginInvoke(() =>

{

textBlock1.Visibility = Visibility.Collapsed;

});

}

private void button1_Click(object sender, RoutedEventArgs e) {

// The click of the button will invoke the background worker.

backgroundWorker = new BackgroundWorker();

backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);

backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker_RunWorkerCompleted);

backgroundWorker.RunWorkerAsync();

}

void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {

// Do nothing here. This method is called when the back ground worker ends its execution.

}

void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) {

// The call to the web service is made on a separate thread which reduces the load on your primary UI thread.

Dispatcher.BeginInvoke(() =>

{

textBlock1.Visibility = Visibility.Visible;

});

TopMoviesSoapClient client = new TopMoviesSoapClient();

client.GetTop10Completed += new EventHandler<GetTop10CompletedEventArgs>(client_GetTop10Completed);

client.GetTop10Async();

}

Windows Phone and Web Services

2011-10-23T11:06:00.000-07:00

This blog covers how a Windows Phone Application can interact with web services available on the Internet. The web services can either be hosted in your corporate data centers which can be accessed by outside world (by placing them on Extranet) or they can be placed on Public Internet either by using Cloud Platforms like Windows Azure or Cloud Infrastructures like Amazon Web Services or you can go ahead and buy yourselves a web domain on various sites like GoDaddy.com etc.

In this blog, i will share the know-how of how to access a publicly available web service via phone with an example - I will use one of the web services which is present on the internet which lists down the top 10 movies of all time. The URL of the web service is - http://www.kirupafx.com/WebService/TopMovies.asmx

The problem statement is - We want to show the list of these movies on the phone.

Solution approach is to access the data via this web service and then bind the data to a list box on the Silverlight based Windows Phone Application.

This can be accomplished via following steps -
1. We need to create a proxy file corresponding to the web service using SLSVCUTIL.exe (SL - Silverlight, SVCUTIL - Service Utility). The SLSVCUTIL is a command line utility provided to the windows phone developers for free when they install the Windows Phone SDK. This utility is present in -
C:\Program Files (x86)\Microsoft SDKs\Windows Phone\v7.0\Tools (64-bit platforms)
C:\Program Files\Microsoft SDKs\Windows Phone\v7.0\Tools (32 - bit platforms)

Open the Visual Studio 2010 Command Prompt as an administrator and enter the following command (make sure you are in Tools directory) -

slsvcutil.exe http://www.kirupafx.com/WebService/TopMovies.asmx

Synatax being slsvcutil.exe <Path of the web service>

See the screenshot below -

If the command is successfully executed, you will see something like the following on the command prompt -

Two files are generated within the tools directory-
a. Proxy file which has the metadat informaiton of the web service (TopMovies.cs)
b. ServiceReferences.clientconfig which is the configuration file used on the runtime to invoke the web service's operations

2. Add the proxy file, configuration files and DLLs within a Windows Phone project -

Either create a new windows phone project or in your existing project, add the proxy and configuration file.

Also, don't forget to add the two DLLs needed by Windows Phone project to interact with web services -
System.Runtime.Serialization.dll and System.ServiceModel.dll (Both are installed by default when Windows Phone SDK is installed and can be added in project by right clicking on Windows Phone project and choosing Add reference...)

3. Use the proxy file to call the web service and get the data -

Proxy file is nothing but the metadata of the actual web service. It will tell you what are the operations exposed by the web service, what are the input and output parameters of those exposed methods, what are the data contracts of the web service etc. The configuration file is used at the runtime. When you use the proxy file and call a method present in the file, at runtime, the call is made to the actual web service using the A (address present in the config file) on the protocol defined by B (binding present in the config file) using contracts defined by C (contracts present in config file).

In this example, the configuration file generated is the following -

<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="TopMoviesSoap" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647">
<security mode="None" />
</binding>
</basicHttpBinding>
</bindings>
<client>
<endpoint address="http://www.kirupafx.com/WebService/TopMovies.asmx"
binding="basicHttpBinding" bindingConfiguration="TopMoviesSoap"
contract="TopMoviesSoap" name="TopMoviesSoap" />
</client>
</system.serviceModel>
</configuration>

As depicted in the configuration file, the web-service is exposed on the URL address of http://www.kirupafx.com/WebService/TopMovies.asmx.
The "basicHttpBinding"binding depicts that the service is accessible on HTTP protocol and the information being passed into and from web service is in clear text. Security mode of None depicts that the web service is accesible to anyone (Anonymous access).
The contract being exposed is correpsonding to TopMoviesSoap.

If you check the proxy file (TopMovies.cs), there is a class named - TopMoviesSoapClient which has a set of methods - GetTop10MoviesAsync and GetTop10MoviesCompleted.

Remember, whenever we are calling a web service via Silverlight application, the communication is always asynchronous. The pattern for asynchronous call is Fire and Forget model. If the operation name is XXX, then from client, we call the method "XXXAsync" which calls that particular operation of the web service in an asynchronous fashion. Once the XXX operation is completed on web service end and it has given back the response to the client the methid "XXXCompleted" is invoked where you can retrieve the result and do whatever UI manipulation you intend to.

To invoke the web service, you need to write down the following piece of code -

TopMoviesSoapClient client = new TopMoviesSoapClient();

client.GetTop10Completed += new EventHandler<GetTop10CompletedEventArgs>(client_GetTop10Completed);

client.GetTop10Async();

In the above code, when the GetTop10Async method is called, the web service's GetTop10 method is called asynchronously. Once this method completes, the return values are captured in GetTop10Completed method.

The rest of the code is pretty straight-forward -

On the designer window, add a listbox named "ListBox1" and in the GetTop10Completed method, add the following lines of code to bind the incoming data to the listbox control -

www.kirupafx.com.ArrayOfString resultSet = e.Result;

listBox1.ItemsSource = resultSet;

Application Life Cycle in Windows Phone 7 Part IV

2011-01-05T12:59:00.001-08:00

Phew! It should be last post for the Application Life Cycle series -

Summary till now – In the Page’s OnNavigatedFrom event, we are saving the state of the elements in State (PhoneApplicationService.Current.State) or known as Transient Storage. State is IDictionary<string,object> and is stored in main memory of the Windows Phone 7. In the Page’s OnNavigatedTo event, we will read the State (Transient Storage) and populate the the elements on the page.

Application Life Cycle Events -

The Launching event is the first event which is raised when a new instance of application is invoked. The file “Notes.dat” is checked; if it is present then we will de-serialize the collection of TravelNotes and set the DataContext of the application.

private void Application_Launching(object sender, LaunchingEventArgs e)
        {
            using (IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication())
            {
                if (file.FileExists("Notes.dat"))
                {
                    using(IsolatedStorageFileStream stream = new IsolatedStorageFileStream("Notes.dat",FileMode.Open,file)) {
                        XmlSerializer serializer = new XmlSerializer(typeof(ObservableCollection<TravelNotes>));
                        App._noteCollection = serializer.Deserialize(stream) as ObservableCollection<TravelNotes>;
                    }
                }

            }
            RootFrame.DataContext = App._noteCollection;
        }

The Closing event is called when the application exits graciously. We are saving the notes collection in “Notes.dat” file (Isolated Storage / Permanent Storage) -

private void Application_Closing(object sender, ClosingEventArgs e)
        {
            using (IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream("Notes.dat", FileMode.Create, file))
                {
                    XmlSerializer serialier = new XmlSerializer(typeof(ObservableCollection<TravelNotes>));
                    serialier.Serialize(stream, App._noteCollection);
                }
            }
         }

The De-Activated event is called when the application is interrupted. We are saving the NoteCollection in transient state before a different application is activated -

private void Application_Deactivated(object sender, DeactivatedEventArgs e)
       {
           PhoneApplicationService.Current.State.Add("NoteCollection", App._noteCollection);
       }

The Activated Event is called once the interruption is over, or when the user presses the back key (after pressing Start or Search key). In this event, we are reading from the transient storage and assigning the datacontext of the application -

private void Application_Activated(object sender, ActivatedEventArgs e)
       {
          object noteCollection = null;
          ObservableCollection<TravelNotes> travelNotes = null;
          if (PhoneApplicationService.Current.State.TryGetValue("NoteCollection", out noteCollection))
          {
              travelNotes = noteCollection as ObservableCollection<TravelNotes>;
              App._noteCollection = travelNotes;
              RootFrame.DataContext = App._noteCollection;
          }
          else
          {
              RootFrame.DataContext = null;
          }
       }

So, thats all!

Before signing off, i want to cover some things -

1. Add a public static variable in App.xaml.cs -

public static ObservableCollection<TravelNotes> _noteCollection = new ObservableCollection<TravelNotes>();

2. Add the following methods in Page1.xaml.cs -

When the second page loads, the List Box’s ItemSource is set with Collection.

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
       {
           notesListBox.ItemsSource = App._noteCollection;
       }

3. public void Go_Home(object sender, EventArgs e) {
NavigationService.Navigate(new Uri("/MainPage.xaml", UriKind.RelativeOrAbsolute));
}

The above method handles click event of the icon button on the Application Bar.

Now try the following scenarios -

1. Save a note. Close the application. Re-run the application and go to “View Notes”. The previous notes should show.

2. Be on the first page and simulate interruption and check if the state to which the first page returns is the same previously.

Application Life Cycle in Windows Phone 7 Part III

2011-01-05T12:20:00.001-08:00

In the third part (TRINITY) of Application Life Cycle in Windows Phone 7, we will build a simple “Travel Diary” application and implement Application Life Cycle events to reinforce the concepts we have discussed in previous two parts.

The logic in the “Travel Diary” application is simple as seen from the screen-shots below -

In the first page of the application, the user can write down the note and choose from one of three options given in the application bar -

1. Save – The user can save the note to a Persistent storage on the phone

2. Reset – The user resets the text entered in the text boxes and decides to re-write.

3. View Notes – The user wants to read his/her previous saved notes or diary entries and he/she navigates to the second page of the application.

First Step – UI of the pages :

a. First Page “Travel Diary” -

Change the Application Title and Page Title of the first page to “Windows Phone 7 Application” and “Travel Diary” respectively.

Add the text blocks and text boxes on the page

Add a new folder “Images” to the project and add 4 images from “C:\Program Files\Microsoft SDKs\Windows Phone\v7.0\Icons\dark” folder – appbar.back.rest.png, appbar.cancel.rest.png, appbar.feature.search.rest.png and appbar.save.rest.png. Right click on the images to change the Build Action from Resource to Content.
Add an application bar to the page and use the icon buttons – appbar.cancel.rest.png, appbar.feature.search.rest.png and appbar.save.rest.png.

<phone:PhoneApplicationPage.ApplicationBar>
      <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
          <shell:ApplicationBarIconButton IconUri="/Images/appbar.save.rest.png" Text="Save" Click="Save_Note"/>
          <shell:ApplicationBarIconButton IconUri="/Images/appbar.cancel.rest.png" Text="Reset" Click="Reset_Note"/>
          <shell:ApplicationBarIconButton IconUri="/Images/appbar.feature.search.rest.png" Text="View Notes" Click="View_Note"/>

      </shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>

Once you follow the above steps, the UI of first page is complete -

b. Second Page “Notes” -

Change the Application Title and Page Title of the first page to “Windows Phone 7 Application” and “Notes” respectively.

Add List-Box on the page -

Add an application bar to the page and use the icon buttons – appbar.back.rest.png
<phone:PhoneApplicationPage.ApplicationBar>
      <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
          <shell:ApplicationBarIconButton IconUri="/Images/appbar.back.rest.png" Text="Go to Home" Click="Go_Home"/>
      </shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>
Once you follow the steps,the UI of the second page is complete -

Application Life Cycle Implementation

There are two places where Application Life Cycle is implemented in Windows Phone 7 Application -

1. At Page Level – OnNavigatedTo and OnNavigatedFrom event of the page

2. At Application Level – Launching, Stopped, Activated and De-Activated events

Important Point – OnNavigatedTo event is the first event of page when it is invoked. Page_Loaded event is the second event fired after OnNavigatedTo event. OnNavigatedFrom event is the last event before the the focus from page is lost (when the application is interrupted with a call, sms, responds to a toast notification, user presses Start or Search hardware key, user navigates to other page).

Important Point – At application level, the first method which is invoked when the application is started is “Launching” event. If the application exits graciously, “Stopped” event is invoked. If the application is interrupted (because of the reasons stated above), Page’s OnNavigatedFrom event is fired first and then Application’s Deactivated event is fired.

Let us first implement the OnNaviagtedTo and OnNavigatedFrom event -

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
       {
           object noteDescription = null;
           object noteName = null;
           if(PhoneApplicationService.Current.State.TryGetValue("NoteDescription", out noteDescription))
           {
               descriptionNoteTextBox.Text = noteDescription.ToString();
           }
           if(PhoneApplicationService.Current.State.TryGetValue("NoteName", out noteName))
           {
               nameNoteTextBox.Text = noteName.ToString();
           }
           base.OnNavigatedTo(e);
       }

protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
       {
           PhoneApplicationService.Current.State.Remove("NoteDescription");
           PhoneApplicationService.Current.State.Add("NoteDescription", descriptionNoteTextBox.Text.Trim());
           PhoneApplicationService.Current.State.Remove("NoteName");
           PhoneApplicationService.Current.State.Add("NoteName", nameNoteTextBox.Text.Trim());

           base.OnNavigatedFrom(e);
       }

Check-Point 1 :

Now, try to put some values in the text boxes and press on Start button which will simulate the “interruption” ; the application will be de-activated (tomb-stoned). If you press the back key now, the first page would open up and the text boxes will have same values before interruption happened. This way you have handled one scenario of TOMB-STONING -

Awesome isn’t it!!

Implement the three Application Bar events -

private void Save_Note(object sender, EventArgs args)
        {
        TravelNotes note = new TravelNotes()
            {
                NoteDescription = descriptionNoteTextBox.Text,
                NoteName = nameNoteTextBox.Text,
                TimeStampOfNote = DateTime.Now
            };
            App._noteCollection.Add(note);
            using (IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream("Notes.dat", FileMode.Create, file))
                {
                    XmlSerializer serialier = new XmlSerializer(typeof(ObservableCollection<TravelNotes>));
                    serialier.Serialize(stream, App._noteCollection);
                }
            }
        }

      private void Reset_Note(object sender, EventArgs args)
        {
            nameNoteTextBox.Text = String.Empty;
            descriptionNoteTextBox.Text = String.Empty;
        }

        private void View_Note(object sender, EventArgs args)
        {
            NavigationService.Navigate(new Uri("/Page1.xaml", UriKind.RelativeOrAbsolute));
        }

These will make sure that when the user clicks on Save button, the record is added to the notes collection and also in Persistent Storage. When the user clicks on View Note button, he/she navigates to the next page and when he/she clicks on Reset button, the values in text boxes are reset.

That’s it for this post. I will implement Application Life Cycle events in the final post for this topic!

Windows Phone Application Life Cycle Part II

2011-01-05T06:13:00.000-08:00

What are the possible life cycle events in Windows Phone 7 Application?

The application runs and stops / closes - Best and rare case scenario in which the user starts the application;faces no interruption and grace-fully exits from the application.
The application runs, tomb-stones and activates back - When the user is running an application and is interrupted by a call, presses "Start" or "Search" button, responds to toast notification, the application de-activates / tombstones. The user presses Back button and the application activates back.
The application runs, tomb-stones and a new instance of application runs - When the user is running an application and is interrupted by a call, presses "Start" or "Search" button, responds to toast notification, the application de-activates / tombstones. The user presses the arrow button on the home page and selects the application. A new instance of application runs.

Example -

You can check the findings by adding the following piece of code in App.xaml.cs -

private void Application_Launching(object sender,LaunchingEventArgs e) {

MessageBox.Show("Launching");

}

private void Application_Activated(object sender,ActivatedEventArgs e) {

MessageBox.Show("Activated");

}

private void Application_Deactivated(object sender,DeactivatedEventArgs e) {

MessageBox.Show("De-activated");

}

private void Application_Closing(object sender,ClosingEventArgs e) {

MessageBox.Show("Closing");

}

In the third part of this topic, we will try implementing the application life cycle in a simple "Travel Diary" application.

Windows Phone Application Life Cycle Part I

2011-01-03T10:57:00.000-08:00

In the first post of the new year, we are going to discuss about probably the most important topic in the Windows Phone 7 Development series - The Application Life Cycle of a Windows Phone Application. We are going to split this topic in multiple parts so that the readers can understand each and everything about it.

In the Part I, we will discuss how a Windows Phone 7 Application's life cycle varies from a life cycle of say a Web Application. We will also discuss the roles of the three hardware keys "Start, Back and Search", available on every Windows Phone 7 device, in the life cycle of Windows Phone 7 application. In Part II, we will go in more detail from code perspective on how a developer needs to handle these application events.

The four states of Windows Phone 7 Application possible are -
1. Running
2. Stopped (Closing)
3. De-Activated (Tombstoned)
4. Activated

Running and Stopped are the two simplest states. When the application starts, it is in "Running" state. Once the end user graciously exits from the application, it is in "Stopped" state.

Important Note - If you are on the first page of the application (in the page-stack) and press "Back" button key, the application exits graciously and goes on "Stopped" / "Closing" state.

Let us take the example of a simple application in which there are two pages - MainPage.xaml and Page1.xaml -

When the user clicks on "Go to next page" button, the second page opens up and when the user clicks on "Back to first Page" button, he/she navigates to the first page.

The page stack is simple, First Page -> Second Page -> First Page and so on.

Now suppose, the user started the application, he is on First Page. At this time, he/she presses the Back key. As, the only page in Page Stack is First Page, the application's Closing event will be called and it will stop.

Suppose, the user is on first page and he/she presses the "Go to NextPage" button. The user navigates to Second Page. The Page Stack is First Page -> Second Page. Now suppose the user clicks on "Go to First Page" button, the Page Stack is First Page -> Second Page -> First Page. Now Back key is pressed. What will happen?

Remember what the Back Key does; it just goes back to the last page of the Page Stack.

In this case, the second page will open up. Press back key again. The first page will open up. Press back key again. Now you are on the first page of the Page stack and there is no page before it, so, the application will close!

Hence, the correct statement would be - "If you are on the first page of the page stack and press Back key, then the application will graciously exit and close"!

Running and Closing is the best and rare case scenario - The Windows Phone Application running without any interruption (SMS, Call etc), will run and when the user decides to graciously exit from the application, the application will close. But in a phone, there will always be interruptions!

What is "Tomb-Stoning"?

When a Windows Phone Application is interrupted by some external event (such as SMS, Call etc.), it goes into a de-activated state (temporary state). Some part of the application stays in the main memory of the phone. When your application is going to be tombstoned it enters a paused state where your application will be given an opportunity to temporary state.

When "Tomb-Stoning" happens?

The user presses on "Start" or "Search" button.
Interruption such as Incoming Call
User responds to a "Toast" notification

Search Button- When the user presses on Search button, the Bing search opens on the Windows Phone 7. The current running application tomb-stones or de-activates. It is developer's responsibilty to save any important data in persistent storage or permanent isolated storage before the application de-activates.

Start Button- When the user clicks on Start button, the current running application de-activates and the user returns to the Home Page of the Windows Phone 7 Application, where the tiles of all the installed applications are visible.

Application Bar and System Tray in Windows Phone 7

2010-12-28T09:40:00.000-08:00

In this post, we will be discussing about the Application Bar and System Tray and their pivotal role while designing your Windows Phone 7 Applications.

Let us first spend some time in understanding what are this visual components -

System Tray

System owned indicator area which displays system-level status information like Battery, Network, Connection to Network, Network provider name, Date Time etc.
The developers can't manipulate the System Tray
The only property exposed in the API is the visibility of the System Tray. Hence, the applications can show/ hide system tray programmatically.

Application Bar

User owned area where application can display icon buttons for most common tasks and menu-items for less common tasks.

Important Points about Application Bar

As mentioned in my previous post on "Creating Theme Aware Applications on Windows Phone 7", if the developer creates an application bar icon button with white foreground and transparent background, the application bar automatically becomes theme-aware. This means that if the user changes the background theme from light to dark and vice - versa, the application bar's background color and foreground color will change automatically!

As seen above in the screen-shots, if you observe the icon button on the application bar and text label below it; they have adapted automatically to the changes made by user in the phone theme.

Windows Phone 7 team mentions that if the Page of the Windows Phone Application supports "PortraitOrLandscape" orientation, the application bar will automatically become "Orientation Aware". However, when i tried doing the same creating a demo application in Visual Studio 2010 Ultimate Edition, the results are different from the claims -

What are different types of elements that can be implemented on Application Bar?
There can be two types of elements that can be implemented on Application bar -

IconButton - This requires the user to enter the Uri of image and also a text label.

The Windows Phone 7 UI Design team recommends you to use icon buttons for performing important tasks on the page
There should not be more than 4 icon buttons in an application bar.
Remember to make the foreground of image as white and background as transparent to make it "Theme Aware"

MenuItem - This requires the user to enter only the text label

Use the menu item for performing less important tasks on the page.
There should not be more than 3 menu items in an application bar.

Opacity of Application Bar

You can also set the opacity of Application Bar from 0 to 1. To improve the performance and UX, it is recommended to keep opacity between 0.5 and 1.

If opacity is 1, displayed page is re-sized to area of screen not covered by the Application Bar.

How to add application Bar in Windows Phone 7 Application?

There are two places in the Windows Phone 7 Application where we can add the Application Bar -

1. In the App.xaml, if the purpose of the Application Bar is to deal with data which is globally exposed.

2. On the Page itself, if the Application Bar needs to interact with the Page-level elements.

Let us add a simple application bar on the page itself to our application with two IconButtons and One MenuItem -

1. First of all, create a new folder in the project and name it as "Images"

2. Add two images to this folder from the location "C:\Program Files\Microsoft SDKs\Windows Phone\v7.0\Icons\dark", named - appbar.add.rest.png & appbar.minus.rest.png

3. Change the "Build Action" property of the images from "Resource" to "Content" so that they can be shown on the Application Bar.

4. Add the following piece of code at the bottom of the page -

<phone:PhoneApplicationPage.ApplicationBar>

<shell:ApplicationBar IsVisible="true" Opacity="0.5" IsMenuEnabled="True">

<shell:ApplicationBarIconButton IconUri="/Images/appbar.new.rest.png" Text="Add" />

<shell:ApplicationBarIconButton IconUri="/Images/appbar.minus.rest.png" Text="Remove" />

<shell:ApplicationBar.MenuItems>

<shell:ApplicationBarMenuItem Text="Exit" />

</shell:ApplicationBar.MenuItems>

</shell:ApplicationBar>

</phone:PhoneApplicationPage.ApplicationBar>

5. On pressing F5, the following will be the UI of application as shown before -

Adding Events to the Icon Buttons and Menu Item

The only event supported on both IconButton and MenuItem is "Click" event.

Add the Click event on the XAML file -

<phone:PhoneApplicationPage.ApplicationBar>

<shell:ApplicationBar IsVisible="true" Opacity="0.5" IsMenuEnabled="True">

<shell:ApplicationBarIconButton IconUri="/Images/appbar.new.rest.png" Text="Add" Click="Add_Click" />

<shell:ApplicationBarIconButton IconUri="/Images/appbar.minus.rest.png" Text="Remove" Click="Remove_Click" />

<shell:ApplicationBar.MenuItems>

<shell:ApplicationBarMenuItem Text="Exit" Click="Exit_Click" />

</shell:ApplicationBar.MenuItems>

</shell:ApplicationBar>

</phone:PhoneApplicationPage.ApplicationBar>

Add the above click events in the code behind file -

private void Add_Click(object sender, EventArgs args) {

// Click event of Add button on Application Bar

}

private void Remove_Click(object sender,EventArgs args) {

// Click event of Remove button on Application Bar

}

private void Exit_Click(object sender, EventArgs args) {

//Click event of Exit Menu Item on Application Bar

}

How do we add Application Bar in App.xaml?

The first question you need to ask is in which scenarios should we add the Application Bar in App.xaml. You can add the ApplicationBar in App.xaml if you have a global data which is accessible across the application.

I believe it is developer's choice whether he/she wants a separate Application Bar on each page or a Application Bars defined for the application in App.xaml.

Developing Orientation Aware Windows Phone 7 Applications

2010-12-26T04:04:00.000-08:00

Like other smart-phones, Windows Phone 7 also supports both Portrait and Landscape Orientations.

In Visual Studio 2010, you can add either Landscape Page or Portrait Page.

There are three types of Orientations that the page in Windows Phone 7 Application can support -

Landscape
Portrait
PortraitOrLandscape

When set to PortraitOrLandscape, when the user rotates the phone, the application re-orientes itself automatically.

Important Note - You can't force re-orientation of the Windows Phone 7 Application. That means if you are holding the device in Landscape orientation, you can't programmatically make the applicaiton to be shown in Portrait Orientation. The developer can only handle the Orientation Changed event raised from the device in the code.

Steps needed for making your application Orientation - Aware

Make the "SupportedOrientations" property of the page as "PortraitOrLandscape" -

2. Make sure that the UI controls are placed in tabular format.(same as in HTML)

3. Place the Grid named "ContentPanel" under the ScrollViewer control -

</Grid>

</ScrollViewer>

4. Run the Application pressing F5.

6. Click on the highlighted button to rotate the emulator in Landscape Orientation.

As you see above, the application has re-oriented itself to Landscape Orientation! Also note that the application bar automatically re-orientes itself when the SupportedOrienations property of the Page is set to "PortraitOrLandscape"

It the page's SupportedOrientations is "PortraitOrLandscape" and the device is rotated so that orientation is changed, the OrientationChanged event of the Page is raised.

OrientationChanged Event of PhoneApplicationPage

private void PhoneApplicationPage_OrientationChanged(object sender, OrientationChangedEventArgs e ) {

}

Let us build another simple application which shows an image on the phone. The code for building such page is as follows -

Now let us implement the OrientationChanged event of the page -

private void PhoneApplicationPage_OrientationChanged(object sender, OrientationChangedEventArgs e ) {

if((e.Orientation == PageOrientation.Landscape) || (e.Orientation == PageOrientation.LandscapeLeft) || (e.Orientation == PageOrientation.LandscapeRight)) {

TitlePanel.Visibility = Visibility.Collapsed;

ContentPanel.SetValue(Grid.RowSpanProperty,2);

ContentPanel.SetValue(Grid.ColumnSpanProperty,0);

}

else if((e.Orientation == PageOrientation.Portrait) || (e.Orientation == PageOrientation.PortraitUp) || (e.Orientation == PageOrientation.PortraitDown)) {

}

So, when the user changes the orientation from Portrait to Landscape the TitlePanel will be made invisible and RowSpanProperty & ColumnSpanProperty is changed.

Lets check it out by actually running the application -

Now change the orientation of the emulator to Landscape -

This is it folks! This is how you can make your Windows Phone 7 Applications "Orientation Aware"

TitlePanel.Visibility = Visibility.Visible;

ContentPanel.SetValue(Grid.RowSpanProperty,1);

ContentPanel.SetValue(Grid.ColumnSpanProperty,1);

Overriding the Back Key in Windows Phone 7 Applications

2010-12-26T02:49:00.000-08:00

In this post we will discuss on how to override the "Back" key behavior in the Windows Phone 7 Applications.
As you must be knowing that every Windows Phone 7 device will have 3 basic hardware buttons-

Back - This has the same behavior as the Back button on our IE browser. It naviagtes user to the immediate previous page present in the page stack. For example - If your application has navigation pattern of Page1 -> Page2 -> Page3 and if you press the back key on Page3, Page2 will open.
Search - This opens up the Bing Search on your Windows Phone 7 device.
Start - This takes the user back to the home screen of the Windows Phone 7 device. Pressing this button will de-activate or tomb-stone your current active application. We will cover more about tomb-stoning in the blogs related to "Application Life Cycle".

When do we want to override the Back key?

May need to override it if "Back to Previous page" is not the logical behavior. For example - When displaying a pop up panel; User would expect Back key to close the panel, not the page.
When the user is on the first page of application and if the Back key is pressed, the application is stopped and taken off the memory. User would expect that a warning message be displayed asking him if he/she is sure to exit from the application.

There can be multiple other scenarios too where you as a developer would want to override the Back key behavior.

How to override the Back Key?

Every Page in Windows Phone 7 Application has an event named "BackKeyPress". We need to override that event to override the default behavior of the Back Key.

private void PhoneApplicationPage_BackKeyPress(object sender, System.ComponentModel.CancelEvenArgs e) {

//Logic to override the default back key behavior

}

Let us understand this with the help of a simple example - You as a developer have decided to show a warning message to the end user if he/she presses the back key on the first page of the application. The pop up warning message will give choice to user if he/she wants to exit the application. If the user clicks on "Yes", the user exits from the application. If the user clicks on "No", the application keeps running.

We need to add the following piece of code in the "PhoneApplicationPage_BackKeyPress" event in the Page -

private void PhoneApplicaitonPage_BackKeyPress(object sender, System.ComponentModel.CancelEventArgs e) {

MessageBoxResult result = MessageBox.Show("Are you sure you want to exit the application","Warning",MessageBoxButton.OKCancel);

if(result != MessageBoxResult.OK) {

e.Cancel = true; // This will negate the default behavior of pressing the back key which is navigating to the previous page.

}

Now let us try running the same "VAT Calculator" application developed in previous posts.

Now press the "Back" key button. The warning message should pop-up -

If the user clicks on "OK" button, the application exits. If the user clicks on "Cancel" button, the application keeps running!

You can add the logic to save the data in Persistent Storage using IsolatedStorage API when the user presses the "Back" key on the first page of Windows Phone 7 Application.

Theme Aware Windows Phone 7 Applications

2010-12-25T11:29:00.001-08:00

In this post, we will discuss how to create Theme - Aware Applications on Windows Phone 7 Platform. The user can select the following on Windows Phone 7 device -

Light and Dark background
Choice between 10 Accent colors

The good news is that Silverlight Controls (which are installed by default when you download Windows Phone 7 Development Kit) are all theme aware (which means that they adapt the color schema and back-ground selected by the user). The developers can make the application "theme-aware" with a little effort!

Let us first create a simple Windows Phone Application which will calculate the VAT Tax (VAT is 12.5% of the total bill!). The following is the UI for the VAT Calculator Application-

As seen in the code, we have added 2 Textblocks, two text boxes, 1 button and also Application Bar. On clicking on the Button, the value present in Food Bill text box is multiplied with .125 and the resulting VAT value is put into the text box corresponding to VAT Tax. The icon button in the Application Bar resets the values in the two text boxes to empty.

Important Note - According to the guidelines published by the Windows Phone 7 design team, the icon images used for the buttons in the Application Bar should be developed with Transparent back-ground and white foreground so that they are theme-aware. Before creating your own icon buttons, you can first check the images in folder "C:\Program Files\Microsoft SDKs\Windows Phone\v7.0\Icons" folder. These images by default are theme-aware and will change according to the background (dark or light) selected by the user on windows phone 7 device.

How to change background color in Phone Emulator to check if the application is Theme Aware?

1. Click on F5 in Visual Studio 2010 to run the application

2. Click on the Back button on the emulator

3. Click on the arrow image highlighted (in red) in the below image -

Click on "Settings"

5. Click on "Theme"
6. Select "Light" as Background (Don't change the accent color as of now!)

7. Go back to the application.
You will notice that the background changes and by default, the textblocks, textboxes, button and icon button on Application Bar have adapted automatically to the change in the theme.

But, how to use the Accent Colors ?
There are default styles available for some of the Silverlight Controls in the {Program FIles}\Microsoft SDKs\Windows Phone\v7.0\Design\ThemeResources.xaml.

To make the TextBlocks, theme aware and make them change their foreground color with change in Accent Color, modify the Style of the textblocks to {StaticResource PhoneTextAccentStyle} (as mentioned in the ThemeResources.xaml).
If you want to make the buttons also change their foreground color on the basis of the accent color, you need to add the following style elements in the App.xaml of the application -

and set the style of the Buttons to the {StaticResource PhoneButtonAccentStyle}.

As shown above, the text blocks as well as the button's foreground color and border colors have changed according to the selection made by the user on the "Accent" colors. The Accent color is available as PhoneAccentColor resource and a brush based on this color is available as PhoneAccentBrush.

Page Navigation in Windows Phone 7

2010-12-25T02:32:00.000-08:00

Before talking about what are the different ways Page Navigation can be implemented in Windows Phone 7, it will be worth-while to spend some time in understanding the concept of Frame and Page.

Frame is the top level conatiner control. PhoneApplicationFrame Class is available in Microsoft.Phone.Controls.dll. It contains the page controls and system level elements such as System Tray and Application Bar.
Page fills up the content region of frame.PhoneApplicationPage class is present in Microsoft.Phone.Controls.dll. It has its own Application Bar too.

Silverlight on Windows Phone 7 uses a Page-based navigation model, similiar to the web page model. Each page is identified by a unique URI and each page is essentially stateless.
The following are the different ways in which Page Navigation can be implemented -

HyperlinkButton's NavigateUri Property
NaviagtionService API
Using QueryString for Page Navigation
Saving the Page State in transient state
Saving the state in Permanent storage

NavigateUri Property of HyperlinkButton - As mentioned earlier, each page in Windows Phone 7 Application is identifed by a unique Uri. By setting the NavigateUri property of HyperlinkButton to the appropriate Uri, navigation can be implemented.

Note that Uri needs to preceed with "/" otherwise exception will be thrown.

NavigationService API - This API has three important methods - Navigate, GoBack & GoForward.

Navigate() - takes Uri as a paramter and navigates to the Uri mentioned as the parameter.
GoBack() - does the same operation as the "Back" key present on Windows Phone 7 device. It navigates to the previous page in the page stack.
GoForward() - navigates to the immediate next page present in the page stack.

Usage of the API Methods - In the button click events, after processing the business logic, these operations can be called.
In the following example, we are adding one button with content "Navigate to next page" and on the "Button1_Click" event, we will be using NavigationService.Navigate method.

The following piece of code needs to be added in button1_Click method -
private void button1_click(object sender, RoutedEventArgs e) {
NavigationService.Navigate(new Uri("/SecondPage.xaml",UriKind.RelativeOrAbsolute));
}
So, now if user clicks on that button on First Page, he/she will navigate to the SecondPage.xaml.

Using QueryString to pass data between pages - If the user wants some piece of data to be passed from one page to another, QueryString parameters can be used in the Uri parameter used in NavigationService.Navigate() method. Lets understand how this works with the following example -

As seen in the screen-shots, the user enters his/her name in the first page of application. After entering the name, when the button with text "Go to next page" is clicked, the second page opens up. The name entered in the first page is also shown on the second page of the application.

How to pass data from one page to another using QueryString parameters?
In the Button1_Click event of first page, the following code needs to be added -
private void button1_Click(object sender, RoutedEventArgs e) {
NavigationService.Navigate(new Uri("/SecondPage.xaml?name="+textBox1.Text.Trim(), UriKind.RelativeOrAbsolute));
}
As seen above, we are passing a paramter in the Uri "name" with value as the text entered in the text box by the user to the second page of application.
In the second page of application, the following piece of code needs to be entered in the PhoneApplicationPage_Loaded event to capture the QueryString parameter passed to it -

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e) {
string name = String.Empty;
NavigationContext.QueryString.TryGetValue("name",out name);
textBlock1.Text ="Welcome " + name + "!";
}
The method NavigationContext.QueryString.TryGetValue(string queryStringParameterName, out string value) reads the Uri and QueryString passed to it. If the QueryString contatins the paramtername then this function will return true and the value in the QueryString parameter will be assigned to the out string parameter. If QueryString does not contain the parameter name, then this method will return false.

You can pass as many parameters as you want from one page to another. The parameter names should be appended with "&" symbol like - "/SecondPage.xaml?name="+textBox1.Text.Trim() +"&address="+textBox2.Text.Trim() and so on.

Using Transient Storage to pass data between pages - Transient Storage is nothing but an IDictionary object with a string as key and object as value. This is accessible through PhoneApplicationService.Current.State object (PhoneApplicationService class is present in Microsoft.Phone.Shell).
One thing to note here is that the value in transient state is available till the life-time of the application. If the application is killed (removed from the main memory), the data in transient storage is lost!
Before going into the topic of how transient storage is used, lets talk about two important overriden methods of the Page -

OnNaviagtedTo - This is the first method which is invoked whenever a page loads. It is called even before PhoneApplicationPage_Loaded event.
OnNaviagtedFrom - This is the method which is called whenever the scope of the page ends. The scope of page can end if the application is de-activated (when a call , email or SMS comes etc.) or when you navigate to other page.

Now, the simple logic to use Transient Storage in order to pass data between pages is as follows -

In the OnNavigatedFrom event of the first page, save the state/data of the page.
In the OnNavigatedTo event of the second page, retrieve the state/data of the previous page

In this application, the first page is Registration Page where the user enters the First Name, Last Name and Email Address. On clicking next, the review page opens and the profile information entered in the first page is shown to the user on this page. The user can check if the information entered is correct and click on Save Profile button to save his/her profile.

The data from the Registration Page to the Review Page can also be sent via QueryString Parameters, but it becomes a little cumbersome if the number of parameters to be passed is greater than 2. Ultimately, it is developer's choice!

Make a class which will store this data -

public class User {

public string FirstName { get; set; }

public string LastName { get; set; }

public string Email { get; set; }

}
2. In the OnNavigatedFrom Event of the "Registration Page" , add the following piece of code -

User user = new User () {

FirstName = textBox1.Text.Trim(),

LastName = textBox2.Text.Trim(),

Email = textBox3.Text.Trim()

};
PhoneApplicationService.Current.State.Add("StateOfFirstPage",user);
3. In the OnNaviagtedTo event of the "Review Page", add following piece of code -

object value;

PhoneApplicationService.Current.State.TryGetValue("StateOfFirstPage",out value);

User currentUser = value as User;

if( currentUser != null) {

firstNameTextBlock.Text = currentUser.FirstName;

lastNameTextBlock.Text = currentUser.LastName;

emailAddressTextBlock.Text = currentUser.Email;

}

Using the Permanent Storage - In Windows Phone 7 as of now, SQL Server Compact Edition is not available. The mode of saving data in a persistent manner can be done through Isolated Storage which is similiar to the File System in our desktop machines.
As discussed earlier, there is no garauntee that the data stored in transient state will remain or not. If your data is very important, consider saving it in persistent/permanent storage (Isolated Storage). The logic of saving and retrieving data is similiar to the one for the persistent state -

In the Registration Page, save the data in Isolated Storage in OnNavigatedFrom event.
In the Review Page, read the data from Isolated Storage in OnNaviagtedTo event.

Important Note - Add System.IO and System.IO.IsolatedStorage to use the APIs for Isolated Storage.

In the OnNavigatedFrom event of Registration Page, the following piece of code will save the data in a file named "Data.dat" -

User user = new User() {

FirstName = textBox1.Text.Trim(),

LastName = textBox2.Text.Trim(),

Email = textBox3.Text.Trim()

};

using (IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication()) {

using(IsolatedStorageFileStream stream = file.OpenFile("Data.dat",FileMode.Create))

{

XmlSerializer serializer= new XmlSerializer(typeof(User));

serializer.Serialize(stream,user);

}

2. In the OnNaviagtedTo event of Review page, the following piece of code will read the data from the file named "Data.dat" -

object value;

using (IsolatedStorageFile file = IsolatedStorageFile.GetUserStoreForApplication()) {

using (IsolatedStorageFileStream stream = file.OpenFile("Data.dat",FileMode.Open)) {

XmlSerializer serializer = new XmlSerializer(typeof(User));

value = serializer.Deserialize(stream);

}

}
User currentUser = value as User;

if (currentUser != null) {

firstNameTextBlock.Text = currentUser.FirstName;

lastNameTextBlock.Text = currentUser.LastName;

emailTextBlock.Text = currentUser.Email;

}

Note - Add System.Xml.Serializer.dll as reference in the project to use XmlSerialier