Reeta S Lodhi's Blog

Autoscaling Application Blocks

noreply@blogger.com (Anonymous) — Thu, 17 May 2012 06:30:00 +0000

Autoscaling Application blocks can automatically scale the Windows Azure application based on the rules defined specifically for the application. The Autoscaling application Block supports two autoscaling mechanisms:

1) Instance Autoscaling, where the block changes the number of role instances based on constraint and reactive rules.

2) Throttling, where the application modifies its own behavior to change its resource utilization based on set of reactive rules. For example switching off non-essential features, or gracefully degrading its UI.

So, there are two types of rules:

1) Constraint rules: Constraint rule set the upper and lower bounds on the number of instances. For example, in evening between 6:00 and 8:00, you need a minimum of 3 instances and a maximum of 7 instances, then use constraint rule.

2) Reactive rules: Reactive rule enables the number of role instances to change in response to unpredictable changes in demand. For example, if workload increases then increase the number of role instances by 1. The reactive rules can use a variety of techniques like performance counters, or windows azure queue length to monitor and control application’s workload. A reactive rule makes changes to the number of role instances only if a constraint rule applies at the same time. It is easy to create a default constraint rule that always applies.

While defining target of an autoscaling rule, you can identify a scale group instead of an individual role. A Scale group enables you to define autoscaling rules that target multiple roles. A scale group can have any number of roles.

Following is an example rule xml. In this there are two constraint rules. One is always active and default constraint. While other only become active at peak time daily at 6 for 2 hours, and overrides the default rule. There are two reactive roles: One will increase the instance count by 1 if the average CPU power usage for last 30 minutes is over 70%, while the other one decrease the instance count by 1 if the average CPU usage for last 30 minutes is less than 30%.

actions>

rule>

actions>

timetable>

rule>

constraintRules>

<when>

when>

actions>

rule>

<when>

when>

actions>

rule>

reactiveRules>

operands>

rules>

Conflicting Rules

1) Conflicting Constraint and Reactive rules: A constraint rule always overrides a reactive rule.

2) Conflicting Constraint rules: If two or more constraint rule includes timetables that specify they are active at the same time then

a) The rule with highest rank is given priority.

b) If two or more constraint rules of same rank conflict, then block will perform the action from first constraint rule it finds.

3) Conflicting Reactive rules: If two or more reactive rules results in conflicting changes to number of role instances then

a) The rule with highest rank is given priority.

b) If two or more reactive rules of same rank conflict, then if any rule suggests increase in number of instances, then largest increase is used.

c) If two or more reactive rules of same rank conflict, then if any rule suggests decrease in number of instances, then lowest decrease is used.

For example if one rule suggest increase the no. of instances by one, another suggest increase the number by two, and another suggest decrease the number by one, then the number will increase by two. Another example, if one rule suggest decrease in number of instances by one, another suggest decrease in number by three, then number of instances will decrease by one.

4) Conflicting actions on scale group: It is possible that multiple rules could suggest different scaling actions on same target at same time, either because same role is member of different scale group or so. In that case, it uses same logic as it is used in conflicting reactive rules.

Queue based messaging in Windows Azure

noreply@blogger.com (Anonymous) — Tue, 15 May 2012 08:26:00 +0000

A typical messaging solution exchanges data between its distributed components using message queues includes publishers publishing messages into queues and subscribers intended to receive messages. The subscriber can be implemented as single- or multi- threaded process, either continuously running or initiated on demand.

At higher level there are two primary queuing mechanism used to enable queue listener (receiver) to receive messages stored on a queue:

Polling or Poll- based model: A listener monitors a queue by checking the queue at regular intervals. A listener is a part of a worker role instance. Main processing logic is comprised of a loop in which messages are dequeued and dispatched for processing. The listener checks for messages periodically. The queue is polled until listener is notified to exit the loop. Windows Azure pricing model measures storage transactions based on requests performed against the queue, regardless if the queue is empty or not.

Triggering or Push- based model: A listener subscribes to an event triggered either by the publisher or by queue service manager, whenever a message arrives on a queue. Then the listener dispatched the message for processing. So, it does not have to poll the queue in order to determine whether any new work is available or not. A notification can be pushed to the queue listeners for every new message, or when the first message arrives to an empty queue, or when queue reaches a certain level. While using Windows Azure Service Bus volume of messaging entities like queue or topics should be considered.

Best Practices for Optimizing Transaction Costs

In queue-based messaging solution, the volume of storage transactions can be reduced using combination of the following methods:

Group related messages into a single larger batch, and compress and stores the compressed image in the blob storage, while keeping a reference of blob in queue.
Batch multiple messages together in a single storage transaction. The GetMessages method in the Queue Service API enables de-queuing the specified number of messages in a single transaction.
While polling, avoid aggressive polling intervals and implement a back-off delay that increases the time between polling requests if a queue remains continuously empty.
Reduce the number of queue listeners – when using a pull-based model, use only 1 queue listener per role instance when a queue is empty. To further reduce the number of queue listeners per role instance to zero, and use a notification mechanism to instantiate queue listeners when the queue receives work items.
If queues remain empty for most of the time, automatically scale down the number of role instances and continue to monitor relevant system metrics to determine if and when the application should scale up the number of role instances to handle increasing workload.
Using a combination of polling and push-based notifications, enabling the listeners to subscribe to a notification event (trigger) that is raised upon certain conditions to indicate that a new workload is put on queue.

Windows Azure Service Bus

noreply@blogger.com (Anonymous) — Fri, 11 May 2012 12:19:00 +0000

Windows azure service bus provides infrastructure for communication, event distribution, naming and service publishing.

Azure Service bus features:

It provides connectivity option for WCF and other service endpoints (including REST endpoints) running behind firewalls and NAT routers, bound to frequently-changing or dynamically-assigned IP addresses.
It enables secure inbound communication from devices outside the firewall.
It provides relayed messaging capabilities. The relay service supports direct one-way messaging, request/response messaging, full duplex messaging, and peer-to-peer messaging.
It provides brokered (asynchronous) messaging capabilities. It supports publish-subscribe and temporal decoupling, i.e., sender and receiver don’t have to be online at same time. It reliably stores message until receiving party is ready to receive message. The core components of brokered messaging are- Queues, Topics and Subscriptions.
It provides a global namespace system that is location- independent, i.e., the name of service in the service bus provides no information about the final destination of the communication.
Provides a service registry for publishing and discovering service endpoint references in a service namespace.
It builds and hosts service endpoints that supports:

a) Exposing a web service to remote users. Expose and secure a local web service in the cloud without managing any firewall or NAT settings

b) Eventing behavior. Listen for notification on any device, anywhere in the world.

c) Tunneling between any two endpoints to enable bidirectional streams.

Deploying on Windows Azure

noreply@blogger.com (Anonymous) — Tue, 27 Dec 2011 06:40:00 +0000

In the previous article we have seen how to create a package for deployment. Now in this article we will see how to deploy it in azure.

1) Open the management portal https://windows.azure.com

2) Click on the Hosted Services, Storage Accounts & CDN tab, and then click Hosted Services, and click New Hosted Service.

3) Now select the subscription. Enter the name of the service and url prefix. Then select a region and do not deploy option. And then click OK. We will create deployment after creating the service.

4) It will start creating hosted service. Once the hosted service is created. You can add certificate and deployment to the service.

5) Now select the Certificates in the newly created hosted service and click Add certificate. Now add the certificate that is used to create remote desktop connections while creating the deployment. Select the certificate and enter password and click OK.

6) Now select the service and click New Staging Deployment.

7) Now enter name of the deployment. Browse for the package file and configuration file and click OK. By default when you package a solution, visual studio will place these file under bin -> Debug -> app.Publish folder.

8) It will start deployment. Once the deployment is ready you can browse to the DNS name of the deployment and can see it.

Creating the Service Model for VM role in Windows Azure

noreply@blogger.com (Anonymous) — Tue, 27 Dec 2011 06:32:00 +0000

Now in this article we will create a service model for the image uploaded in azure.

1) Start Visual Studio 2010. Create new project. From the Visual C# template, click Cloud. Give a name to the project and click OK.

2) Now Click OK, without selecting any role.

3) Now add a new VM role. For this right click the Roles select Add and then select New Virtual Machine Role.

In case if didn’t find the “New Virtual Machine Role”, you have to run the scripts below to add new registry key or just change the following [dword] registry key:

HKEY_CURRENT_USER\SOFTWARE\Wow6432Node\Microsoft\Windows Azure Tools for Microsoft Visual Studio 2010\1.0\VirtualMachineRoleEnabled=1

4) Now in properties of the VMRole, select Virtual Hard Disk tab, and select an account for the VHD. If you are using it for first time then you will not find any account there, and either you have to import or manage it.

5) Now click on manage, It opens a window and then click New.

6) Now select a certificate

7) You can either choose an existing certificate, or can create a new one. To create a new certificate click “Create”. It asks for a friendly name. Give name and click OK.

8) You can view the certificate. Just select the certificate and click View.

9) You can install the certificate and create a .pfx for it. Just click on the Install.

10) Now you have to upload the newly created certificate to the management portal. For this click “Copy the full path”. Now click on the “Window Azure Portal”

11) On the portal, click on the Add Certificate.

12) Now select the certificate, by pasting the path of the certificate. And click OK.

13) Now enter the subscription Id on which certificate is uploaded and click OK.

14) Now select the account and click Close.

15) Now it will try to get the vhd’s of the account. Then select the VHD uploaded.

16) Now configure endpoints to allow external connection. For this click on the Endpoints tab, and then click Add Endpoint. Now define Http as the protocol and port 80 for both public and private ports.

17) Now configure the remote desktop connection for the role. Right click the VM role solution and click Package…

18) Now click the enable Remote desktop for all roles.

19) Now here select an existing certificate or you can create a new one. And enter username and password for remote desktop connection. Also select the expiration date. And then click OK.

20) Now click on the Package.

21) It creates the .cspkg and .cscfg file for deployment. And open the location in windows explorer.

Uploading the Disk Image to Windows Azure

noreply@blogger.com (Anonymous) — Tue, 27 Dec 2011 06:24:00 +0000

In this article we will see how to upload .vhd image to Windows Azure. You cannot upload image directly from the portal, but it can be done through command prompt. To upload image

1) Open Windows Azure SDK Command Prompt as an administrator from Start -> All Programs -> Windows Azure SDK v1.x

2) At command prompt execute the following command

csupload Add-VMImage -Connection "SubscriptionId=; CertificateThumbprint=" -Description "Base image Windows Server 2008 R2" -LiteralPath "" -Name baseimage.vhd -Location

Where

is your subscription Id

is the thumbprint of the certificate on the management portal.

· Set the description as Base image Windows Server 2008 R2

is the full path of the .vhd file.

· Set the name of the image as baseimage.vhd. So, that the name of the image on portal will be baseimage.vhd

set the location where the hosted service will be deployed. The location can be “East Asia”, “North Central US”, “North Europe”, “South Central US”, “Southeast Asia”, “West Europe”.

3) In the Windows Azure VHD Verification Tool dialog, click OK to allow the VHD to be mounted.

4) Now it mounts the .vhd file and verifies it. In this process it generates a compressed file (.preped file) in the same folder as the original image file.

5) After that it creates a new blob for uploading the image file and starts uploading the compressed image to the azure account. It will take significant amount of time. After completion it shows the details.

6) Once the image is uploaded successfully it shows the status of the image as Committed.

Installing Windows Azure Integration Components on VM role

noreply@blogger.com (Anonymous) — Tue, 27 Dec 2011 06:13:00 +0000

In this article we will see how to install integration components on the virtual machine. The integration components must be installed on the machine before base image is uploaded to the Azure. The integration components start each time the OS starts. It handles the integration between the role instance and Azure environment. Windows Azure Integration components support:

· Windows setup for deployment

When a VM role instance comes online, the generalized image that is used to create the instance must run through a setup specialization phase. This specialization phase is performed by the System Preparation Tool (sysprep), provided by the Windows Azure Integration Components. To automate the specialization, it creates an answer file named c:\unattend.xml.

· Interaction with the Windows Azure environment

It installs the Service runtime API’s, so that the VM role can get information about the Azure environment, like instance ID, upgrade domain etc. This information is only available to the code that is running under an Administrator or LocalSystem account in the VM role instance.

· Local storage resources

You can access the local resources using the Service runtime API’s or at c:\Resources\.

· Certificate installation

You can install the certificates to the LocalMachine store location. It is not possible to install certificates to the CurrentUser store location or any other store location. Do not install the certificate before uploading, because while generalizing the image, System Preparation Tool (sysprep) will destroy the private key of the certificate.

Now we will see how to install Integration components on VM role.

1) From the Hyper-V manager, right click the VM role and click Connect, and start it. Now Click on the Media -> DVD Drive -> Insert Disk…

2) Now open the location for wavmroleic.iso. It will be located at C:\Program Files\Windows Azure SDK\v1.6\iso.

3) It opens an AutoPlay dialogue. Now click Open folder to view files using Windows Explorer.

4) Now click double click the WaIntegrationComponents-x64.msi (Windows Installer) file.

5) Click next on the Setup wizard.

6) Now at Operating system Configuration wizard, enter Password and click Next.

7) Now Click Install.

8) If it asks for installing the device software, click Install.

9) It will take some time for installation. When the installation completes, click Finish.

10) Now it will ask you to restart the system. Click Yes to restart the system.

11) Now launch the System Preparation Tool from the location C:\system32\sysprep\sysprep.exe. Set the System Cleanup Action to “Enter System Out-of-Box Experience (OOBE)”, check the option labeled Generalize, set the Shutdown Options to Shutdown, and then press OK.

12) Now the image is ready for deployment.

Preparing Base Image for Deployment

noreply@blogger.com (Anonymous) — Tue, 27 Dec 2011 05:52:00 +0000

Now we had a .vhd image containing default installation of Windows server 2008 R2. Now in this article we will install components required for the deployment to windows azure. Connect to the virtual machine created and starts it.

1) After login, it shows the desktop of virtual machine. Now from All Programs -> Administrative Tools, launch Server Manager.

2) Select the role node and click Add Roles.

3) In the Server Roles step, select the Web Server (IIS), and click Next.

4) Now on the Web Server (IIS) step click Next.

5) On the Role Services step click Next.

6) Now on the Confirmation step, check Web server is included for the installation. And then click Install.

7) When installation is complete, click Close.

8) Next, in Server Manager, select the Features node and then click Add Features. We can see that Web Server IIS tools are already in the features list.

9) In the Features step, expand the .Net framework 3.5.1 Features and tick .Net Framework 3.5.1 and click Next.

10) On the Confirmation step, Click Install.

11) After the features are installed, on Results step, click Close.

12) Now open the Windows Update control panel, and on the Change Settings page, select the option labeled Never check for updates (not recommended) and then click OK.

13) Now check for available updates and install the updates.

Creating a Base image for Virtual Machine Role on Windows Azure

noreply@blogger.com (Anonymous) — Mon, 26 Dec 2011 11:51:00 +0000

Creating a Base image for Virtual Machine Role on Windows Azure

In this article we will see how to create a base image for Virtual machine role on windows Azure. I am assuming you have windows server 2008 R2 and hyper V installed on the server.

1) Open Hyper-V manager and connect to Hyper-V server.

2) Now select the server, then right- click on it. And select New and click Virtual Machine…

3) It opens a New Virtual Machine Wizard. On the Specify Name and Location tab, specify the name for virtual machine. If you want to change location of the image, you can also do this by specifying the new location, and click Next.

4) Now in the Assign Memory step specify the memory allocated to VM. This amount can range from 8MB- 10236 MB. In our demo we will set it to 2048 MB, and click Next.

5) Next, in the Configure Networking step, select Local Area Connection - Virtual Network and then click Next.

6) Next, in the Connect Virtual Hard disk step, select the Create a virtual hard disk. Specify the name of the disk. If you want to change the location you can change it here. Set the size of the disk. If you want to choose an existing disk, you have to choose Use an existing virtual hard disk option, and browse to the disk location. If you are using an existing disk, you can skip the OS installation section.

Note - The image file must contain a single partition with the OS installation and must not include a recovery partition.

7) Now, since we are creating a new disk we need to specify how OS (Windows server 2008 R2 Enterprise Edition) will be installed. Here are different options, either you can install OS later, or can install it from CD/DVD or from a network. Here we are using an .iso image for installing OS. So select the option Install an operating system from a boot CD/DVD-ROM. And select the image file and browse to the location. Now click next.

8) Click finish to create the virtual machine.

9) Now in the Hyper-V it shows the newly created virtual machine. If it not showing then refresh it.

10) Now right click the newly created machine and click Connect… Now click on the start as shown in figure to start the virtual machine.

11) Now it will start installing the windows server 2008 R2 from the specified location. If it doesn’t start installation then might be installation location is incorrect. If the location is correct it asks for choosing language, currency format. Now click next.

12) Click Install Now to start installation.

13) Choose the windows Server 2008 R2 full installation and click Next. And accept the terms and conditions.

14) Now choose the custom installation.

15) When it prompts for installation like

By default installation creates a recovery partition automatically. But for VM role we need only single partition. So to configure it Now press SHIFT+F10 to open command prompt. At command prompt enter following commands:

diskpart

select disk 0

create partition primary

exit

diskpart command will launch the diskpart tool. Now select the disk 0 and make this partition as primary. And exit from the diskpart tool.

Now close the command prompt.

16) Now continue the installation.

17) Once the installation is complete it reboots and ask for login for the first time.

Now enter the login password and continue.

Virtual Machine Role in Windows Azure

noreply@blogger.com (Anonymous) — Mon, 26 Dec 2011 11:38:00 +0000

Virtual Machine Role in Windows Azure

Windows Azure compute provides facility to run an application in the cloud. For this azure provides three types of roles:

1) Web role: used for web application programming and supported by IIS7

2) Worker role: used for asynchronous, long running tasks, without any user interruption.

3) VM role: used for migrating windows server applications to Windows azure in an easy way.

In this article we will see Virtual Machine (VM) roles. VM role fits for the situations where:

· Long running application installation is required

· Error prone application installation

· Application installation needs manual interaction

· Migrating existing applications

VM role is a special role, which gives user freedom to control the operating system. While web role and worker role runs on a virtual machine, but VM is a virtual machine. But this comes with the responsibility of making sure that the OS image is up to date through the creation of difference disks. So it increases the cost of development, testing and maintenance.

Creation of VM role in azure needs:

I will blog each step in detail in my upcoming articles.

Difference between ASP.NET HttpHandler and HttpModule

noreply@blogger.com (Anonymous) — Fri, 14 Oct 2011 07:09:00 +0000

In this blog we will see what are http handlers and modules. And in which condition which one is suitable. For that first we need to understand when user request application resource to web server, what happened? The user requests for a resource on web server. The web server examines the file name extension of the requested file, and determines which ISAPI extension should handle the request. Then the request is passed to the appropriate ISAPI extension. For example when an .aspx page is requested it is passed to ASP.Net page handler. Then Application domain is created and after that different ASP.Net objects like Httpcontext, HttpRequest, HttpResponse are created. Then instance of HttpApplication is created and also instance of any configured modules. One can register different events of HttpApplication class like BeginRequest, AuthenticateRequest, AuthorizeRequest, ProcessRequest etc.

HTTP Handler

HTTP Handler is the process which runs in response to a HTTP request. So whenever user requests a file it is processed by the handler based on the extension. So, custom http handlers are created when you need to special handling based on the file name extension. Let’s consider an example to create RSS for a site. So, create a handler that generates RSS-formatted XML. Now bind the .rss extension to the custom handler.

HTTP Modules

HTTP Modules are plugged into the life cycle of a request. So when a request is processed it is passed through all the modules in the pipeline of the request. So generally http modules are used for:

Security: For authenticating a request before the request is handled.

Statistics and Logging: Since modules are called for every request they can be used for gathering statistics and for logging information.

Custom header: Since response can be modified, one can add custom header information to the response.

Logging Application Block

noreply@blogger.com (Anonymous) — Thu, 13 Oct 2011 10:08:00 +0000

First we need to know what application blocks are?
Application Blocks are reusable software components and are part of Microsoft’s Enterprise Library. Enterprise library provides configurable features to manage crosscutting concerns like validation, logging, exception management etc. Here I elaborate on one of the feature of Enterprise Library- Logging Application Block. One can use the Logging Application Block to log information to:

1) Event logs

2) A text file

3) An email message

4) A database

5) A message queue

6) Windows Management Instrumentation (WMI) event

7) Customize the logging location

In this article we will see how to configure the logging. One need to install the Enterprise Library.

Create a windows form application. Now add a reference of Enterprise Library Logging Application Block to the solution.

Now add a configuration file for configuring the log. Now edit it with Enterprise Library Configuration.

It opens a window. In that select Blocks -> Add Logging Settings

It creates a default logging settings as follows:

It contains a category named “General”, which is using an “Event Log Listener” with a “Text Formatter”. For now we can leave Special Categories. So, what all these are doing?

Let’s understand it with an example. There may be some logs which you need to write in event log and a text file, and for some log you need to mail also. So you create one category which writes all logs to event log and text file, and another category for sending mail of only error logs. Then you have to create 3 listeners, for logging in event log, text file and mailing. You can also define different formatters for different type of listeners. For example you need a detailed log for logging in events log and precise log for mailing. All these settings are defined in the configuration. All you need to do is when you write a log just defines the category of the log and rest is done by the application block.

Categories:

Category can filter the log entry and route it to different listeners. The filter can be based on the severity, i.e., Critical, Error, Warning or Information.

Logging Target Listeners:

Different listeners can be defined here. We only need to do configuration and these listeners can write to event logs, a flat file, xml file, to database, send mail etc.

Log Message formatters:

This is used to define a format in which log is written. Text formatter is the default formatter, which writes all the information. For customizing the formatter, define a template.

A sample project is uploaded. This contains a general category which logs to event logs and a flat file using text formatter. And mail category which sends mail using mail formatter. And depending on the conditions it logs to general category, or sends mail, or can do both.

So now you can see a configuration section “loggingConfiguration” in the app.config file.

This configuration section contains listeners, formatters, categorysources and specialSources. One can configure listener, formatter, categories here.

To write a log you just need to create a LogEntry and specify the category. Of category is not specified, log will be written to default category.

So, now you can see logging so easy using Application blocks.

Managed Extensibility Framework (MEF)

noreply@blogger.com (Anonymous) — Mon, 19 Sep 2011 05:58:00 +0000

MEF is a component of .net framework 4.0, to create lightweight, extensible applications. It avoid hard dependencies and lets application developer to discover and use extensions without any configuration required.

Why MEF?

Imagine a situation where an application is using several smaller components. And application is responsible for creating and running those components.

One possible solution could be including all the components as source code in the application. But you cannot add new components without modifying the source code.

Another solution could be to provide an interface for decoupling between application and components. So the component can implement the interface and interact with application. But this approach too has drawback. As application cannot discover components by itself, it must be explicitly told which components are required and loaded.

Here MEF comes into the picture. MEF provides a way to discover components via composition. A MEF component specifies both its dependencies (known as imports) and what capabilities (known as exports) it makes available.

Let’s understand it with the help of an example. Suppose you are having a simple calculator application which currently supports addition and subtraction.

Creating composition container and catalogue

Composition container keeps track of which components are available for composition and what are their dependencies. It provides a way by which application can get the instance of components to be composed. We need to include System.ComponentModel.Composition in reference.

    //An aggregate catalog that combines multiple catalogs

    var catalog = new AggregateCatalog();

    //Adds all the parts found in the same assembly as the current class

    catalog.Catalogs.Add(new AssemblyCatalog(typeof(this).Assembly));

    //If parts are placed at some other location then adds that directory path

//catalog.Catalogs.Add(new DirectoryCatalog(componentsDirectoryPath));

    //Create the CompositionContainer with the parts in the catalog

    CompositionContainer _container = new CompositionContainer(catalog);

    //Fill the imports of this object

try

        this._container.ComposeParts(this);

    catch (CompositionException compositionException)

        Console.WriteLine(compositionException.ToString());

catalog.Catalogs.Add(new AssemblyCatalog(typeof(this).Assembly));

This adds the components from the current assembly. To add the components from some specified folder location, add a directory catalogue like:

catalog.Catalogs.Add(new DirectoryCatalog(componentssDirectoryPath));

Where componentsDirectoryPath is the path of directory where components can be found.

Import and Exports

Define an interface like it.

[Import(typeof(IOperation))]

public interface IOperation

{

string Operate(int leftOperand, int rightOperand);

}

This interface has an attribute Import. This ImportAttribute defines that the type IOperation needs to be imported. So we implement the IOperation class, and above the class we use ExportAttribute indicating that it has the capabilities of IOperation. Also it contains ExportMetadata attribute indicating that depending on the metadata Symbol the operation is performed.

[Export(typeof(IOperation))]

[ExportMetadata("Symbol", '+')]

class Add : IOperation

//Implementation of IOperation

Now we will do lazy initialization for getting objects like this:

[ImportMany]

IEnumerable<Lazy<IOperation, IMetadata>> operations;

Lazy initialization is used so that only operations that are needed are initialized. Based on the metadata it initializes what operation is to be performed. It contains ImportMany attribute because IOperation can be filled by many exports like add, subtract etc.

Lazy Initialization

As we see we declare an IEnumerable for lazy initialization. Now how does it work? When we run application, it initializes the catalogue and creates a container. Based on the Import attribute it finds the components which can be filled for it. Here we have only one class Add to fill it. So operations will contains only single Lazy object, and that object will be initialized when it will be accessed first time. So based on the operation we will call Operate function.

foreach (Lazy i in operations)

        if (i.Metadata.Symbol.Equals(operation))

                 result= i.Value.Operate(left, right).ToString();

I had a sample project to illustrate it. It contains 2 operations Add and Subtract in the assembly and Multiplication in a separate dll, which can be found in “\Extensions” folder.

Extension Methods in .Net

noreply@blogger.com (Anonymous) — Thu, 21 Jul 2011 08:29:00 +0000

In this article we will see what extension methods are, why we need them and how to create them.
Extension methods are methods which allow you to extend a type, even if you don’t have the source code for that type. Let’s understand it with a simple example: Suppose you want to add IsNumeric method to string class to check whether a string is numeric or not. What you will do?
1) Either you have to create a new class inheriting from string class and then add the IsNumeric method in it. Now this solution has 2 problems. First, what if the class you want to inherit, in this case string class, is sealed. You can’t inherit from it. Second, if any how you inherit the string class then you need to make sure everyone else is using your class not the string class
2) Or create a static StringHelper class and create a static IsNumeric function in it. But this solution also has a problem that user need to know a Helper class exist.
Prior to .Net Framework 3.5 second solution was the most popular solution. But in .Net Framework concept of extension methods is introduced. Now let’s see how to create extension methods. We need to create a static class StringHelper and a static method IsNumeric as we do in the second solution.
public static class StringHelper
{
public static bool IsNumeric(this string str)
{
double val;
return double.TryParse(str, out val);
}
}
The only difference from second solution is the “this” keyword in the IsNumeric parameter. By using this keyword we are indication that it is the extension of type next to the “this” keyword. Here we have written “this string” it means IsNumeric is the extension of string type.
To use it:
string nonNumericString = "123abc";
bool Result = nonNumericString.IsNumeric();
Another benefit of using extension method is that you can easily convert helper class into extension methods without breaking the existing functionality, i.e., following code still works:
bool Result = StringHelper.IsNumeric(nonNumericString);
So now you realize it is easy to create extension methods. J

Initializing Windows Azure Diagnostic – Part 2

noreply@blogger.com (Anonymous) — Sat, 07 May 2011 16:54:00 +0000

As you have read in my previous article how to initialize Windows Azure diagnostic monitor. Now we will see how to collect different diagnostic data. I am defining a connection string for the role. For that right click on the role and click on properties. Now from the connection tab you can add configuration string.

1) Collecting data from event logs
Open the Role entry point class. Add following code to the OnStart() function
var config = DiagnosticMonitor.GetDefaultInitialConfiguration();
config.WindowsEventLog.DataSources.Add("System!*");
config.WindowsEventLog.ScheduledTransferLogLevelFilter = LogLevel.Warning;
config.WindowsEventLog.ScheduledTransferPeriod = TimeSpan.FromMinutes(1.0);
DiagnosticMonitor.Start("DiagnosticsConnectionString", config);

So, first you need to get DiagnosticMonitorConfiguration object. Then you can add channel to the datasource. You can add multiple channels. Windows Azure cannot log Security channel. You can define log level filter, so that only those logs are transferred. You have to define schedule transfer period, so that after that time span logs are transferred to the account you specified in the configuration. Now start the diagnostic monitor with the connection and new configuration.

2) Collect data from Performance Counters
Open the Role entry point class. Add following code to the OnStart() function

var config = DiagnosticMonitor.GetDefaultInitialConfiguration();
config.PerformanceCounters.DataSources.Add(new PerformanceCounterConfiguration()
{
CounterSpecifier = @"\Processor(_Total)\% Processor Time",
SampleRate = TimeSpan.FromMinutes(1.0),
});
config.PerformanceCounters.ScheduledTransferPeriod = TimeSpan.FromMinutes(5.0);
DiagnosticMonitor.Start("DiagnosticsConnectionString", config);

Here I have defined a performance counter which takes sample for processor time in every minute. You can add multiple performance counters in the data souce. And then transfer the log to azure account defined in the connection string after every 5 minutes.

3) Collect data from IIS logs
IIS logs are collected only for web role because worker and VM roles don’t run under IIS.
To enable IIS logging add following code to the web.config.

<tracing>
<traceFailedRequests>
<add path="*">
<traceAreas>
<add provider="ASP" verbosity="Verbose" />
<add provider="ASPNET" areas="Infrastructure, Module, Page, AppServices" verbosity="Verbose" />
<add provider="ISAPI Extension" verbosity="Verbose" />
<add provider="WWW Server"
areas="Authentication, Security, Filter, StaticFile, CGI, Compression, Cache, RequestNotifications, Module"
verbosity="Verbose" />
</traceAreas>
<failureDefinitions statusCodes="400-599" />
</add>
</traceFailedRequests>
</tracing>
After adding this code IIS logs are automatically logged. No additional API calls are required.

4) Collect data from crash dumps
In the role entry point class add the following code;

Microsoft.WindowsAzure.Diagnostics.CrashDumps.EnableCollection(true);

Pass true for enabling complete crash dump data, or false for partial crash dump data.

Initializing Windows Azure Diagnostics- Part 1

noreply@blogger.com (Anonymous) — Sat, 07 May 2011 14:49:00 +0000

As we have seen in my previous blog that some of diagnostics data is stored in table, while some in blob. For collecting diagnostics data, we must initialize Windows Azure diagnostic monitor. Windows Azure diagnostic monitor runs in Windows Azure and in the compute emulator and collects diagnostic data for a role instance. Only Windows Azure Logs, Windows Azure Diagnostic Infrastructure Logs and IIS logs are configured in the diagnostic monitor by default. We can collect other diagnostic data by importing diagnostic module. A role instance that imports the Diagnostic module starts, it starts the diagnostic monitor.
To start diagnostic monitor for a role open the role entry point class and make sure that you are using Microsoft.WindowsAzure.Diagnostics namespace in the class. Now on the Azure service project right click on the role and click Properties. Here I am configuring a web role.

Now in the configuration section check enable diagnostics. And specify the account credentials

You can either use development storage or can give your account credentials. Just click on “…” and will ask for the credentials.

Now when you open your .cscfg file it has a new setting for the webrole like
<ConfigurationSettings>
<Setting name="Microsoft.WindowsAzure.Plugins.Diagnostics.ConnectionString" value="DefaultEndpointsProtocol=https;AccountName=myaccountName;AccountKey=myAccountKey" />
</ConfigurationSettings>

And in the .csdef file it import the module like:
<Imports>
<Import moduleName="Diagnostics" />
</Imports>

If you are using a web role or worker role template for creating roles then in the web.config or app.config following code is added. Or you can just inherit a class from RoleEntryPoint and add the following code in the config file.

<system.diagnostics>
<trace>
<listeners>
<add type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="AzureDiagnostics">
<filter type="" />
</add>
</listeners>
</trace>
</system.diagnostics>

If you want to create a web role just override OnStart() method, and if you want to create a workerrole override OnStart() and Run() method. We will see it in my next article.

Understanding Diagnostics in Windows Azure

noreply@blogger.com (Anonymous) — Fri, 11 Mar 2011 17:11:00 +0000

Windows Azure diagnostics provides facility to store diagnostics data. Azure diagnostics supports logging and monitoring of diagnostics data. It uses blob service or table service to save diagnostics data, depending on the diagnostics data. Before logs are saved in a container they are indexed in WADDirectoriesTable table in the storage account.
Following diagnostics data is stored in table storage:

*Data Source*	*Table name in Azure Storage*	*Detail*
Windows Azure Logs	WADLogsTable	These are the application logs dumped from the application.
Windows Azure Diagnostics Infrastructure Logs	WADDiagnosticInfrastructureLogsTable	These are the logs about running of diagnostics service.
Windows Event logs	WADWindowsEventLogsTable	These are the logs generated on the instance where logs are running.
Performance counters	WADPerformanceCountersTable	These are the performance matrices like memory utilization, processor utilization, response time etc.

Following diagnostics data is stored in blob storage:

*Data Source*	*Container name in azure storage*	*Detail*
IIS Logs	wad-iis-logfiles	These are the IIS logs generated by role instances.
Failed Request Logs	wad-iis-failedreqlogfiles	These are the IIS failed requests logs generated by role instances.
Crash Dumps	wad-crash-dumps	These are the logs generated on the application crash.

Deploying an application in Windows Azure

noreply@blogger.com (Anonymous) — Wed, 09 Mar 2011 05:54:00 +0000

In the previous article we have seen how to create a Hello World application in azure. In this article we will see how to deploy it in Windows azure. To deploy an application in azure, two files are needed- a package file and a configuration file. Configuration file is already in CloudService1 named ServiceConfiguration.cscfg. Now for the package file just right click on the CloudService project and click Publish.

Then it asks to create just a package file or to deploy it in azure.

If first option is selected then it creates the package file and opens the explorer.

Once we have a package file (.cspkg) and configuration file (.cscfg) then we can deploy it through management portal, or azure service management cmdlets, or Cerebrata’s CloudStorageStudio, or Cerebrata’s Azure management cmdlets. We can directly upload it through visual studio also, if we select second option from publish dialog. It needs a subscriptionId and a X509 v3 certificate as shown below:

Then we have to provide deployment environment and storage account.
Whichever option we had selected, we need:
a) A Windows Azure Subscription – when we sign up for azure, a subscription is associated with our live Id.
b) A Windows Azure Hosted Service – we need to create a hosted service for deployment. It provides two deployment environment- production and staging.
c) A Windows Azure storage account – When we deploy through visual studio then package file is first uploaded in blob storage of the storage account, and then deployed from the blob service.
So summarizing deployment through management portal in some simple steps:
1) We need a package file and a configuration file to deploy.
2) To create a package file click publish and create package only option from project.
3) Sign In the management portal.
4) Create a new hosted Service if you want to deploy in a new service.
5) Then in deployment environment either deploy in production or staging.
6) Then start the deployment.
7) You can see the progress of the deployment on the portal
8) To delete a deployment first click on stop, and when it is stopped delete it.

Creating a “Hello world” application in Azure

noreply@blogger.com (Anonymous) — Tue, 01 Mar 2011 07:11:00 +0000

In this article we will see how to create a “Hello World!!!” application in azure in .net. I had used Visual Studio 2010 along with azure SDK 1.3 installed. Start visual studio and select a new project. In the cloud template select Windows Azure Cloud Service.

Once you click OK. It asks for selecting a Role. Here we are adding an ASP.Net Web role.

It will create two projects- CloudService1 (Azure Service Project) and WebRole1 (ASP.net Project). The Azure service project is used to configure the application, and to create a deployment package. ASP.Net project is like a normal web project.

Here I removed header div from the SiteMaster.

And add a text “Hello World!!!!” in the default.aspx

And we are done. Now Select Cloud Service as your startup project and run it. When you run it, azure simulation environment is initialized, and it starts development storage and development fabric.

And here you can see your Hello World!!!

If you select WebRole1 as your startup project and run the solution. It will run as a normal ASP.Net project and hosted locally on localhost.
If you click on the Azure Simulation and select “Show development Fabric UI” then it will show the azure services running on your machine.

Here My CloudService1 is running having a single instance of WebRole.

Overview of Windows Azure

noreply@blogger.com (Anonymous) — Thu, 24 Feb 2011 07:39:00 +0000

Windows Azure

Windows azure is Microsoft’s cloud platform. It includes Windows Azure operating system that serves as the Platform-as-a-Service (PAAS) and Infrastructure-as-a Service (IAAS). In order to understand AAS lets take an example-

1) To deploy or use software we first need servers, firewalls, switches etc.

2) Once server is setup then we need an OS then application server or database.

3) Then we have to install the actual application.

So we need some infrastructure, then platform and software. Windows Azure provides platform and infrastructure by providing a scalable and cost-effective computing, storage and networking resources on demand.

Windows Azure has three main components in azure: Compute, Storage and Fabric.

1) Windows Azure Compute:

Windows azure provides hosting environment for managed code. It provides computation service through roles. Windows azure supports 3 types of roles:

a) Web roles used for web application programming and supported by IIS7

b) Worker roles used for background processing of web roles.

c) Virtual Machine (VM) roles used for migrating windows server applications to Windows azure in an easy way.

Within a subscription one can have zero or more hosted service. Each hosted service can have deployment- either production or staging. And each deployment can have one or more roles of any types. Each role can have multiple instances.

2) Windows Azure Storage:

Windows azure provides storage in cloud. It provides 4 types of storage services:

a) Queues for messaging between web roles and worker roles.

b) Tables for storing structural data.

c) BLOBs (Binary Large Objects) to store text, files or large data.

d) Windows Azure Drives (VHD) to mount a page blob. These can be uploaded and downloaded via blobs.

3) Windows Azure AppFabric:

AppFabric provides infrastructure services for developing, deploying and managing Windows azure application. It provides 5 services:

a) Service bus It provides secure connectivity between distributed and disconnected applications in cloud.

b) Access control It grants access control to application and services based on the identity user. So the authorization decisions are pulled out from application into a set of rules that can transform incoming security claims into claims that applications understand.

c) Caching It provides caching for high speed access, scaling, and high availability of data to application. It is available for developer preview only.

d) Integration It provides integration between windows azure application and other SAAS. It will be available by CTP 2011.

e) Composite App It provides a hosting environment for WCF web services and workflows. It will be available by CTP 2011.

Creating commands in powerShell

noreply@blogger.com (Anonymous) — Mon, 28 Jun 2010 12:28:00 +0000

Learn how to create commands in few simple steps:
For creating commands in powerShell, I had installed templates for it, which I get from here: http://channel9.msdn.com/ShowPost.aspx?PostID=256835. There are VB.NET and C# ones.

1) Now select a powerShell project as shown:

The project contains a PSSnapin file and a reference to the assembly System.Management.Automation
2) In the PSSnapIn.cs fill information as required.
[RunInstaller(true)]
public class WindowsPowerShell1SnapIn : PSSnapIn
{
public override string Name
{
get { return "MyFirstSnapIn"; }
}
public override string Vendor
{
get { return "Reeta"; }
}
public override string VendorResource
{
get { return "WindowsPowerShell1,"; }
}
public override string Description
{
get { return "Registers the CmdLets and Providers in this assembly"; }
}
public override string DescriptionResource
{
get { return "WindowsPowerShell1,Registers the CmdLets and Providers in this assembly"; }
}
}
3) Now add a new cmdlet class.

4) In this cmdlet we simply add a value to a parameter and output it.
[Cmdlet(VerbsCommon.Get, "Hello", SupportsShouldProcess = true)]
In this attribute “Get” is our verb and “Proc” is subject. Different verbs can be used. Read http://msdn.microsoft.com/en-us/library/ms714428(VS.85).aspx for more information.
5) To add parameter write :
[Parameter(Position = 0,
Mandatory = true,
ValueFromPipelineByPropertyName = true,
HelpMessage = "Enter a name")]
[ValidateNotNullOrEmpty]
public string Name
{
get;
set;
}
To validate a parameter we can add different attribute on a parameter. We can add help message for the parameter By “HelpMessage”. We can indicate that a parameter is mandatory by adding “Mandatory= true”. We can add position for a parameter.
6) Now add a code to write the parameter value in ProcessRecord(). When this command runs it execute code written in Processrecord().
WriteObject will write values on the commandlet.
7) For running the power shell we first need to install the dll.
On visual studio command prompt use - installUtil yourAssemblyPath.dll
8) Now add the SnapIn in the power shell using command:
Add-PSSnapin MyFirstSnapIn

9) Now get the registered SnapIn list by command :
Get-PSSnapIn –registered
10) Now run the command using:
Get-Hello –Name Reeta
It will output – Hello Reeta
Since we had written position in the Parameter attribute we don’t need to specify –Name. if we write- Get-Hello Reeta, it gives same output.
If we don’t provide any parameter then it says that it is mandatory.
These are just simple steps for creating a command in powerShell. I get help from this blog http://blogs.msdn.com/b/daiken/archive/2007/02/07/creating-a-windows-powerShell-cmdlet-using-the-visual-studio-windows-powerShell-templates.aspx

How to create a Captcha

noreply@blogger.com (Anonymous) — Fri, 26 Feb 2010 11:26:00 +0000

Step 1: Create a new website. In Default.aspx page put this code:
<table>
<tr>
<td>
<img height="30" alt="" src="BuildCaptcha.aspx" width="80" />
</td>
</tr>
<tr>
<td>
<asp:TextBox runat="Server" ID="txtCaptcha"/>
</td>
<td>
<asp:Button runat="Server" ID="btnSubmit" OnClick="btnSubmit_Click" Text="Submit" />
</td>
</tr>
</table>
Step 2: In Default.aspx.cs page write this code for Submit button click:
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (Page.IsValid && (txtCaptcha.Text.ToString() == Session["RandomStr"].ToString()))
{
Response.Write("Code verification Successful.");
txtCaptcha.Text = string.Empty;
}
else
{
Response.Write("Please enter code correctly.");
}
}
Step 3: Now add a new Page named BuildCaptcha.aspx.
On this page we choose random numbers and create a bitmap image from them. To do this write this code on the page load:
protected void Page_Load(object sender, EventArgs e)
{
//That is to create the random # and add it to our string
Bitmap objBMP = new Bitmap(60, 20);
Graphics objGraphics = Graphics.FromImage(objBMP);
objGraphics.Clear(Color.YellowGreen);
objGraphics.TextRenderingHint = TextRenderingHint.AntiAlias;
//' Configure font to use for text
Font objFont = new Font("Arial", 8, FontStyle.Italic);
string randomStr = "";
char[] myArray = new char[5];
int x;
Random autoRand = new Random();
for (x = 0; x < 5; x++)
{
myArray[x] = System.Convert.ToChar(autoRand.Next(65, 90));
randomStr += (myArray[x].ToString());
}
//This is to add the string to session, to be compared later
Session.Add("RandomStr", randomStr);
//' Write out the text
objGraphics.DrawString(randomStr, objFont, Brushes.Blue, 3, 3);
//' Set the content type and return the image
Response.ContentType = "image/GIF";
objBMP.Save(Response.OutputStream, ImageFormat.Gif);
objFont.Dispose();
objGraphics.Dispose();
objBMP.Dispose();
}
Now you are done. When you run website it looks like this:

How to read RSS and atom feed

noreply@blogger.com (Anonymous) — Fri, 20 Nov 2009 12:14:00 +0000

Before .Net 3.5 we had to go for separate framework to read the feeds and parse it. In that case we need to refer the framework in our project and install that assembly in Bin or GAC. We need to parse RSS and atom feeds separately. But now, with .Net 3.5, life has become much easier.
With the namespace 'System.ServiceModel.Syndication' it is just few lines of code to read and parse the feeds either RSS or Atom. Just have a look on the code:
string Link;
string Copyright;
StringBuilder rssFeed= new StringBuilder();
XmlReader reader = XmlReader.Create(url);
SyndicationFeed feed = SyndicationFeed.Load(reader);
String Title = feed.Title.Text;
if (feed.BaseUri != null)
{
       Link = feed.BaseUri.ToString();
}
else
{
       Link = feed.Links[0].Uri.ToString();
}
if (feed.Copyright != null)
{
      CopyRight = feed.Copyright.Text;
}
rssFeed.Append(“Title: ”+Title);
rssFeed.Append(“Link: “+Link);
rssFeed.Append(“\nCopyRight: “+CopyRight);
foreach (var item in feed.Items)
{
    string title = "";
    string description = "";
    string link = "";
    DateTime PublishDate;
    String AuthorName;
    String AuthorUri;
   if (item.Title != null)
   {
        title = item.Title.Text;
   }
   if (item.Content != null)
{
    description = ((System.ServiceModel.Syndication. TextSyndicationContent)(item.Content)).Text;
   }
   else
   {
         if (item.Summary != null)
         {
               description = item.Summary.Text;
         }
    }
    if (item.Links != null && item.Links.Count > 0)
    {
          link = item.Links[0].Uri.ToString();
          for (int i = 1; i < item.Links.Count; i++)
          {
                 link += "\n" + item.Links[i].Uri.ToString();
           }
     }
     if (item.PublishDate != null)
    {
         PublishDate = item.PublishDate.DateTime;
     }
     if (item.Authors != null && item.Authors.Count > 0)
    {
           StringBuilder Authors = new StringBuilder(item.Authors[0].Name + ",");
          StringBuilder AuthorsUri = new StringBuilder(item.Authors[0].Uri + ",");
         for (int i = 1; i < item.Authors.Count; i++)
        {
                Authors += "\n" + item.Authors[i].Name + ",";
                AuthorsUri += "\n" + item.Authors[i].Uri + ",";
      }
     AuthorName = Authors;
      AuthorUri = AuthorsUri;
   }
    rssFeed.Append(“\n\nLink: ”+link);
    rssFeed.Append(“\nTitle: ”+title);
   rssFeed.Append(“\nDescription: ”+ description);
   rssFeed.Append(“\nPublishDate: ”+ PublishDate.ToString();
   rssFeed.Append(“\nAuthorName: ”+ AuthorName.ToString();
   rssFeed.Append(“\nAuthorUri: ”+ AuthorUri.ToString();
}

Asynchronous Event Handling

noreply@blogger.com (Anonymous) — Sat, 19 Sep 2009 08:42:00 +0000

Asynchronous Event handling
Why need Async Event Handling?
Let’s consider an example that you need some data in your application. So you call a method GetData(…) and it will give you the data. But untill you get the data your UI Thread is blocked. So you need something like that you call the method GetData(…) and return, and when data is done an event is raised to the UI that OK I am done and you process the data.
So here are the simple steps for Asynchronous event handling:
Suppose that I had a class “Myclass” which contains a mehod “GetData” which I want to call asynchronously, So that it raise an event when it get all the data without blocking main thread.
Step 1: Create MyEventArgs.cs
First decide what you parameters are needed after Get Data Return. These are the properties in MyEventArgs class. Suppose that we need a UserState, Result, and if any exception occurs then Error. So my class will look like this:
public class MyEventArgs
{
public object Result { get; set; }
public Exception Error { get; set; }
public object UserState { get; set; }
}
Above the class I define a delegate eventhandler like this:
public delegate void MyEventHandler(object sender, MyEventArgs e);
Step 2: Create MyEventController.cs
For asynchronous handling we create a delegate for the method. It has the same parameters as in Myclass’ s GetData method. If the GetData has some out parameters then we can also use them. If not then no need to define out parameter.:
public delegate object MyEventDelegate(string param1,out Exception Excep);
Now define a controller class like this:
public class MyEventController
{
public event MyEventHandler MyEventComplete;
MyEventDelegate _MyEventDelegate;
MyClass myClass;
public MyEventController()
{
myClass = new MyClass ();
_ MyEventDelegate = new MyEventDelegate(MyMethod);
}
private void OnMyEventComplete(MyEventArgs e)
{
if(MyEventComplete !=null)
{
MyEventComplete(this,e);
}
}
public void GetData(string param1, object UserState)
{
Exception Excep = null;
object[] _AsyncUserStats = new object[1];
_AsyncUserStats[0] = UserState;
_MyEventDelegate.BeginInvoke(param1, out Excep, new AsyncCallback(MyMethodCallBack), _AsyncUserStats);
}
private object MyMethod(string param1, out Exception exception)
{
return myClass.GetData(param1,out exception);
}
private void MyMethodCallBack(IAsyncResult ar)
{
Exception Excep = null;
AsyncResult aresult = (AsyncResult)ar;
object Result = ((MyEventDelegate)aresult.AsyncDelegate ).EndInvoke(out Excep, ar);
object[] _AsyncUserState = ar.AsyncState as object[];
MyEventArgs result = new MyEventArgs()
{
Error=Excep,
Result =Result,
UserState = _AsyncUserState[0],
};
OnMyEventComplete(result);
}
}
Let’s see what happens in the controller class. It define an event MyEventComplete which will be raised when GetData complete. For this we define a function “OnMyEventComplete” which raise the event when we get all the data. It also defines an object of the delgate we define above “MyEventDelegate”. In the constructer we register the method (MyMethod here) with the delegate which we want to call. In this method we actually call the GetData of MyClass.
Now look at the GetData of MyController class. This is the method which we call when we want to get the data. In this method we call the BeginInvoke of the delegate. In the BeginInvoke it accepts the same parametrs as in the GetData metod of MyClass and two extra parameters of type AsyncCallback and object or object[]. The AsyncCallback contains the method which will be called when it gets the data. The syntax for implementation of this callback method is :
private void MyMethodCallBack(IAsyncResult ar)
And in the MyMethodCallBack we get the result and raise the event by calling OnMyEventComplete method.
So the flow is like this:

In the UI we create a class of the controller and call the GetData of controller. Event “MyEventComplete” will be raised when get Data complete. Before calling the method you have to register the event like this :
MyEventController _myController= new MyEventController();
_myController.MyEventComplete += new MyEventHandler (myController_MyEventComplete);
void myController_MyEventComplete(object sender, MyEventArgs e)
{
this.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal, (Action)(() =>
{
/////.. event is raised and we get the result in the e.Result
}));
}
Since this event complete is returned in another thread we neet to use Dispatcher like above.
And when we need the data we use _myController.GetData(….);

.NET RIA Service

noreply@blogger.com (Anonymous) — Fri, 28 Aug 2009 13:04:00 +0000

.Net RIA Services bring together the ASP.NET and Silverlight platforms. It provides a pattern to write application logic that runs on the mid-tier. It integrates with Silverlight components on the client and ASP.NET on the mid-tier. Get more information about RIA services from http://www.nikhilk.net/NET-RIA-Services-Vision-Architecture.aspx.
In this blog we see how to create a simple .NET RIA Service enabled project. It only provides a brief overview of.Net RIA Services.
Step 1: First Create a new Silverlight Project as:
Step 2: Then enable .Net Ria Services like this:

Step 3 : Now to mid-tier i.e., on RiaTest.Web project add a new item and select the Data category as follows:

we will access the Northwind database using the Entity Framework. We choose 2 tables from the northwind for this application.

Step 4 : After building project create a DomainService on the mid-tier. A DomainService is a class that exposes entities and operations for a specific data domain. It is also where the developer adds application logic. To create a Domain Service Add new item to the mid-tier and in the Web category add DomainService class as follows:

Step 5 : Now we select only one table Orders , we will not set Enable Editing for the table because we want only read only table. Generate metada will create metadata of table on client.

It will generate a class as follows:

It has following characteristics:
· It is derived from LinqToEntitiesDomainService, an abstract base class built into the .NET RIA service framework3.
· It is bound to NorthwindEntities1 class we created earlier
· A single GetOrders() query method is generated because we select only Orders table
· This.Context.Orders in GetOrders() will give all the order in table.
· OrderService is marked with [EnableClientAccess] indicating it is visble on client tier
When we build project and click on Show all files on client tier we see some Gnerated code as:

This is the client proxy class which is generated from the Domain service class which we create on mid-tier.
Step 6 : Now in MainPage.xaml add a data Grid named “MyGrid” as follows:

Don’t forget to include System.Controls.Data.dll in references.
Step 7 : Now in MainPage.xaml.cs add 2 references :
· System.Windows.Ria.Data
· RiaTest.Web
Now create an object of OrderContext and then load entities of Orders and set the itemsource of the datagrid.

When you run the project you see all the orders in the data grid.