Programmers' corner

Visual Studio 2012 Update 1

2012-12-02T21:59:00.002+01:00

It's now possible download Update 1 for VS 2012. Most of the new functionality appears in Ultimate and Premium and primarily spans these four areas:

Windows development
SharePoint development
Agile teams
Continuous quality

More info here:
http://www.microsoft.com/visualstudio/ita/visual-studio-update#story-update-1

WCF Data Service and Knockoutjs

2012-08-01T22:48:00.000+02:00

One of the strengths of modern websites is the use of client side technologies.In fact there are several libraries that can help us develop our work and are among the most popular jQuery.

Using these libraries we can more easily interact with the DOM (Document Object Model) than using the traditional JavaScript functions.

Furthermore, the ajax functions are much simpler to implement.

With jQuery, you can do many things, but not all ... or you can do them but some become very complex, such as dynamically create an html select tag.

Here a very basic example with jQuery:

//a simple continents array
someContinents = { "1": "EUROPE", "2": "AMERICA", "3": "ASIA", "4": "AFRICA" };

$.each(someContinents, function (k, v) {
$('select#selContinents').append($("").attr("value", k).text(v));
});

With a foreach jQuery function ($.each) we can iterate all elements (continents). Every iteration append an "option" html tag (with key and value) to html select tag. This is a very very simple example. Your data can come from several sources (webservice, array...).

Now introduce another way to populate a combo box, using less JavaScript code and a very powerful library: Knockout. It does not replace jQuery, but we can say that it can be an integration.

But we go one step at a time…

First, we create a sample table on a MS SQL database called “T_STATE” with two columns: id and description. Then populate it with some data like these:


Data table

This will be out data source. Now create a new ASP.NET application (or a MVC, one or the other is indifferent).

Add a new ADO.NET Entity Data Model and add the previous database table to its designer. That’s result:


Entity

I saved my Entity Container Name as “DbTestEntities”. Normally, I prefer to create a new libray project and create a new ADO.NET Entity Model inside it, so I can reuse it in other applications. Remember our saved name because it will serve for the next step: WCF data service.

Now we see how to interact with data stored on a database and client-side components. I decided to use the DataService because they are easy to implement, and through the OData protocol can be queried directly from the URL when calling the service. Of course you can also use other traditional REST webservices, but in this example we’ll use a WCF Data Service.

On Visual Studio 2010 project, add a new WCF Data Service. A new *.svc file will be created on our project. I saved it as “WcfDS.svc” Open this file and modify class code with parameters previous created in our entity model designer:

public class WcfDS : DataService<DbTestEntities>

{

public static void InitializeService(DataServiceConfiguration config)

{

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

config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;

}

It’s important that DataService base class is of the type described on the entity container name. Remember, my previous name was “DbTestEntities”, so base class will be DataService.

The other step is to set entity set access rule:

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

First parameter will be the exact entity name (in my example it’s T_STATE) and right “AllRead”. These settings permit a read only permission in the table.

Press F5 to debug our project, navigate to our WCF Data Service Page (ex http://localhost:1340/WcfDS.svc/) and you can see something like this (it depend on used browser):

<service xml:base="http://localhost:1340/WcfDS.svc/"><workspace><atom:title>Default</atom:title><collection href="T_STATE"><atom:title>T_STATE</atom:title></collection></workspace></service>

Right! Now try to read T_STATE entity data through browser url http://localhost:1340/WcfDS.svc/T_STATE and result source data will be something like this:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<feed xml:base="http://localhost:1340/WcfDS.svc/" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom">
<title type="text">T_STATE</title>
<id>http://localhost:1340/WcfDS.svc/T_STATE</id>
<updated>2012-07-31T20:29:12Z</updated>
<link rel="self" title="T_STATE" href="T_STATE" />
<entry>
    <id>http://localhost:1340/WcfDS.svc/T_STATE(1)</id>
    <title type="text"></title>
    <updated>2012-07-31T20:29:12Z</updated>
    <author>
      <name />
    </author>
    <link rel="edit" title="T_STATE" href="T_STATE(1)" />
    <category term="DbTestModelNs.T_STATE" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/xml">
      <m:properties>
        <d:id m:type="Edm.Int32">1</d:id>
        <d:State>ITALY</d:State>
      </m:properties>
    </content>
</entry>
<entry>
    <id>http://localhost:1340/WcfDS.svc/T_STATE(2)</id>
    <title type="text"></title>
    <updated>2012-07-31T20:29:12Z</updated>
    <author>
      <name />
    </author>
    <link rel="edit" title="T_STATE" href="T_STATE(2)" />
    <category term="DbTestModelNs.T_STATE" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/xml">
      <m:properties>
        <d:id m:type="Edm.Int32">2</d:id>
        <d:State>USA</d:State>
      </m:properties>
    </content>
</entry>
<entry>
    <id>http://localhost:1340/WcfDS.svc/T_STATE(3)</id>
    <title type="text"></title>
    <updated>2012-07-31T20:29:12Z</updated>
    <author>
      <name />
    </author>
    <link rel="edit" title="T_STATE" href="T_STATE(3)" />
    <category term="DbTestModelNs.T_STATE" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/xml">
      <m:properties>
        <d:id m:type="Edm.Int32">3</d:id>
        <d:State>GERMANY</d:State>
      </m:properties>
    </content>
</entry>
<entry>
    <id>http://localhost:1340/WcfDS.svc/T_STATE(4)</id>
    <title type="text"></title>
    <updated>2012-07-31T20:29:12Z</updated>
    <author>
      <name />
    </author>
    <link rel="edit" title="T_STATE" href="T_STATE(4)" />
    <category term="DbTestModelNs.T_STATE" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/xml">
      <m:properties>
        <d:id m:type="Edm.Int32">4</d:id>
        <d:State>GREECE</d:State>
      </m:properties>
    </content>
</entry>
<entry>
    <id>http://localhost:1340/WcfDS.svc/T_STATE(5)</id>
    <title type="text"></title>
    <updated>2012-07-31T20:29:12Z</updated>
    <author>
      <name />
    </author>
    <link rel="edit" title="T_STATE" href="T_STATE(5)" />
    <category term="DbTestModelNs.T_STATE" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/xml">
      <m:properties>
        <d:id m:type="Edm.Int32">5</d:id>
        <d:State>FRANCE</d:State>
      </m:properties>
    </content>
</entry>
</feed>

You can get detailed information on this site OData protocol: http://www.odata.org/

If this is ok, we can proceed with the most interesting argument: how to read and use these data in a drop down list created by

To do this, we need to download jQuery library and Knockout. We can found them here:

http://jquery.com/

http://knockoutjs.com/

Then, as other library we need to reference these libraries in the html head tag. Suppose our path is in the script website directory, code will be following (in the example I use MVC 3 and Url helper):

We note that before we create a reference to the jQuery library, then Knockout. In this way we can ensure that any jQuery functions can be called and recognized with Knockuot. Now we can create JavaScript code to retrieve data and populate our drop down list (html select tag).

First we need to declare a class that represents our data. In this case, we need two fields: id and state name:

function StateDef(data) {

this.id = ko.observable(data.id);

this.State = ko.observable(data.State);

}

Data parameter represent single data read from webservice. Now create a new ViewModel JavaScript function and bind it into Knockout library:

function StatesViewModel() {

}

ko.applyBindings(new StatesViewModel());

Here StatesViewModel code:

function StatesViewModel() {

var self = this;

self.states = ko.observableArray([]);

self.selectedState = ko.observable();

$.getJSON("../../WcfDS.svc/T_STATE", function (res) {

var mappedStates = $.map(res.d, function (item) { return new StateDef(item) });

self.states(mappedStates);

})

.error(function (err) { alert(err.responseText); });

} //end ViewModel

We create a new states variable and initialize it with an obserbableArray. The, with jQuery getJSON function we read all States data through WCF Data Service.

Note two things inside $.getJSON function: we use a $.map function to retrieve datas and “translate” them in the object we want, in this case transform them in our State definition (with StateDef function). Second thing is res.d variable. It represents data collection read from data service, so “item” is a single state object.

All of our mapped data will become our array of data to pass to select html control.

That’s complete JavaScript code:

function StateDef(data) {

this.id = ko.observable(data.id);

this.State = ko.observable(data.State);

}

// Overall viewmodel for this screen, along with initial state

function StatesViewModel() {

var self = this;

self.states = ko.observableArray([]);

self.selectedState = ko.observable();

$.getJSON("../../WcfDS.svc/T_STATE", function (res) {

var mappedStates = $.map(res.d, function (item) { return new StateDef(item) });

self.states(mappedStates);

})

.error(function (err) { alert(err.responseText); });

} //end ViewModel

ko.applyBindings(new StatesViewModel());

</script>

Last part consists of create our html select tag and bind it with Knockout data:

With “option” tag we connect previous states array. “value” is our selected item and “optionsText” represent our State description.

In follow example I explain another kind to create a html select tag connected to Knockout data:

</select>

In this example, I used a foreach iteration on states array. Then I create a single html option tag and bind it with id and State data.

If we want to show select tag only if there are elements, we can add another parameter to data-bind select:

</select>

“Visible” in this case will be true only if exists at least one item in states array.

If you want to extend the use of Knockout and see all the potential, potetre go on the official website: http://knockoutjs.com/

Lista terremoti recenti

2012-07-09T22:12:00.000+02:00

http://www.windowsphone.com/it-IT/apps/ad03ceb0-86b4-4053-96d9-70b3fb6d5497

Ignore inline DTD in XML file with LINQ to XML

2012-02-07T22:47:00.000+01:00

If we want to read an XML file with LINQ to XML that have DTD inline instructions, normally we use this statement

XDocument doc = XDocument.Load("myXmlFile.xml");

but... we'll receive an exception.

The Load method of the XDocument has several overloads, including one in particular that takes as a parameter an XmlReader object.
Let's see how to use it:

XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Ignore;
XmlReader reader = XmlReader.Create("myFile.xml", settings);
XDocument doc = XDocument.Load(reader, LoadOptions.PreserveWhitespace);

First, create a XmlReaderSettings object and set its DtdProcessing property to "Ignore". It causes the DOCTYPE element to be ignored.

Then, create a new XmlReader object using the file path name and XmlReader previously created settings.

Now we can open without previous exception out xml file, passing XmlReader object as argument of XDocument Load method.

EntityDataSource and isolation level.

2012-01-16T23:31:00.000+01:00

Suppose we have a asp.net page and display some data from a database table in a GridView. The latter is connected to EntityDataSource.
If we are running a long elaboration on that table (as an update or other processing), the page containing the data to show cannot hang and display our data until processing is finished.

That's not ever that we want....

Probably this behavior is not what we want. How can we solve it?

Using EntityDataSource ContextCreated event we can "attach" a transaction to the ObjectContext used by datasource.

protected void MyEntityDataSource_ContextCreated(object sender, EntityDataSourceContextCreatedEventArgs e) {
        e.Context.Connection.Open();
        e.Context.Connection.BeginTransaction(IsolationLevel.ReadUncommitted);
}

First we have to manually open the database connection. Then, start a database transaction specifying the isolation level we want to use. In this case, we need "ReadUncommitted" so we can read all data from database, including those not yet committed (dirty).

Web data storage API HTML5

2011-11-30T08:19:00.001+01:00

Look this tip (italian language only):
Web data storage API HTML5 Look

Reportistica in ASP.NET con la libreria Spire.DataExport

2011-11-23T10:01:00.003+01:00

Look this article (italian language only):

Reportistica in ASP.NET con la libreria Spire.DataExport

Trace T-SQL statements generated by Entity Framework

2011-11-17T22:08:00.006+01:00

If we want to keep track of a query with Entity Framework without use a profiler, we can use the method ToTraceString which is part of the ObjectQuery object. In practice, this method displays the commands sent from our T-SQL query to the database.

First, when using the ToTraceString method we need an open connection to the database, otherwise we will raise an exception.

Its use is very simple. Here an example:

using (MyEntities ctx= new MyEntities()) {  var strSql = "SELECT VALUE t FROM MyEntities.Employees AS t";  var myQuery = ctx.CreateQuery(strSql);   ctx.Connection.Open();   Console.WriteLine(myQuery.ToTraceString());  Console.ReadLine();}

The output will be something like:

SELECT

[it].[FirstName] AS [FirstName],

[it].[LastName] AS [LastName], 

[it].[Age] AS [Age]

FROM [dbo].[Employees] AS [it]

One important thing about ToTraceString method is that it doesn’t execute the query but it's only output the statement to be executed.

Layout for multiple file upload with jQuery

2011-07-24T12:53:00.001+02:00

Within forms, many times we need to empower users to enter one or more files. In some cases you may need to perform the upload of multiple files, without knowing in advance how they might be.
Limit the number of inputs for uploading files is sometimes not the best choice, so we could give the user a chance to put other files in his complete autonomy.

This post explains how to use jQuery without any plugins for creating html for inserting multiple fileupload.

We start from a simple html page that contains only those elements essential for this application:

<!DOCTYPE html>
<html>
<head>
    <title>Multiupload file</title>
    <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script>
    <script type="text/javascript" src="Scripts/JScript.js"></script>
</head>
<body>

    <div class="container">
        <button id="btAddFileUpload" type="button">Add file</button>
        <div id="fileUp1">
            <input id="File1" type="file" />
            <button id="btDelete1" type="button" value="1" onclick="javascript:deleteUpload(value)">Delete</button>
        </div>

        <input id="Submit1" type="submit" value="Submit" />
    </div>

</body>
</html>

I copied into my "Scripts" directory latest jQuery library version, but you can refer it in the classic mode by Google:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script>

I wrote my JavaScript code in an external file called "JScript.js" and referenced in html script tag. This is the code:

$(document).ready(function () {
    $('#btAddFileUpload').click(add);
});

//upload file tags counter
var count = 1;

//add fileupload method
function add() {

    //upload file tags increase
    count++;

    //clone div tag with all children elements
    var copied = $('#fileUp1').clone(true);

    //increase all children tags ids
    $('input:file', copied).attr('id', 'File' + count);
    $('button', copied).attr(
        { id: 'btDelete' + count,
          value: count
        }
    );

    //increase div tag id
    $(copied).attr('id', 'fileUp' + count);

    /* another mode to change attribute names
    copied.children('input').attr('id', 'File' + count);
    copied.children('button').attr('id', 'btDelete' + count);
    */

    //append copied div and relative children tags in container div, but before submit button
    $(copied).appendTo('.container').insertBefore('#Submit1');
}

//delete method fileupload method
function deleteUpload(id) {

    //remove file upload (parent div and childrens)
    if (count > 1) {

        //decrease total amount of uploadfile tags
        count--;

        var nameElemToDelete = '#fileUp' + id;
        $(nameElemToDelete).remove();
    }

    //to avoid holes, recalculating all the ids after the removed one
    for (indx = id; indx <= count; indx++) {

        var inputDiv = $('#fileUp' + (parseInt(indx) + 1));
        $(inputDiv).attr('id', 'fileUp' + indx);

        $('input:file', inputDiv).attr('id', 'File' + indx);
        $('button', inputDiv).attr(
            { id: 'btDelete' + indx,
              value: indx
            }
        );
    }
}

At the begin, I call the $(document).ready jQuery statement to join the add function to add button at the startup (page entirely loaded).
Each time you click on the button "btAddFileUpload", all you clone the "

" tag including its children, renaming the id attributes with a new name including the number increases by one.
All this is done using the jQuery methos "clone" on an object (tag) that you want to replicate.

With "deleteUpload" function you can delete the same tag (and all its childrens) and recalculate all ids to avoid holes. This was done to iterate over all the inputs file without any problems.

C# - read range of dates without considering all holidays

2011-06-22T20:51:00.006+02:00

The problem
I need to calculate the elapsed days between a date and the other, regardless of public holidays and national holidays.

The idea
The first thing to do was to remove from the range of dates on Saturdays and Sundays, in order to consider only working days.
For national holidays but I thought I'd use a database table containing a list of dates as smalldatetime fields.
But I did not want every year to update all the dates of the table, only to set the new year. So I decided to set any date on the database with a fixed year 2011 (but I could also use more than one year 'recently).
The only date to be updated every year is the Easter holiday because it is considered a date "variable".

This is the table:

My solution
Calculating the difference (in days) between the end date and the start and this would eliminate any other festive dates, according to Saturdays and Sundays and holidays are based on. However, if a holiday falls in one of these two days, obviously the date is eliminated once.

This is the C# code:

public static int GetDateDiff(DateTime start, DateTime end) {

TimeSpan dsDiff = end - start;

int diff = dsDiff.Days;

int diff2 = diff;

if (diff <= 0)

return diff;

using (var ctx = new MyEntities()) {

  //run a cycle on any date, from start to finish

  for(int i = 0; i <= diff2; i++) {

   DateTime dtTemp = start.AddDays(i);

       //a cycle on any holiday date

                 foreach (var t in ctx.T_HOLIDAYS) {

   int yearDiff = t.date.Year - dtTemp.Year;

   TimeSpan ts = t.date - dtTemp.AddYears(yearDiff);

                        if (ts.Days == 0 && t.date.DayOfWeek != DayOfWeek.Saturday && t.date.DayOfWeek != DayOfWeek.Sunday) {

    diff--;

    break;

   else if (dtTemp.DayOfWeek == DayOfWeek.Saturday || dtTemp.DayOfWeek == DayOfWeek.Sunday) {

    diff--;

    break;

  }//end foreach

 }//end for

Reading file with LINQ.

2009-10-31T17:22:00.000+01:00

LINQ, the new extension in the Microsoft Framework 3.5 very often is very powerful. Today I tried to read a big txt file (104 Mbytes, 5 millions rows).

For first, I created a new Console application in C# .NET 3.5. In the main method i wrote this code:

//start time
long start = Environment.TickCount;
var query = from a in File.ReadAllLines(@"C:\reading_test.txt")
select a;
foreach (string s in query)
;

Console.WriteLine("With ReadAllLines: " + (Environment.TickCount - start).ToString() + " ms");

When executed it on my machine, time result was 3313 ms.

The File.ReadAllLines() method sometimes is useful, but not performant. Infact with a line code only we can read all lines of a file. But there's a problem: if your input file is very big, you'll have a huge wast of memory.
In my example, when this application start memory used was about 17Mb, but after the query was 360Mb !!
This means all read lines are holdings in memory.

I solved this problem in this way:

long start = Environment.TickCount;
using (StreamReader sr = new StreamReader(@"C:\reading_test.txt")) {
var query = from x in sr.GetLines()
select x;
foreach (string s in query)
;
}
Console.WriteLine("With Extension Method: " + (Environment.TickCount - start).ToString() + " ms");

This is my code for GetLines() extension method:

static class ExtensionsClass {
public static IEnumerable GetLines(this StreamReader sr) {
String line;

if(sr == null)
throw new ArgumentNullException();

while((line = sr.ReadLine()) != null)
yield return line;
}
}

The query operator is implemented as an extension method for the StreamReader class. It enumerates the lines provided by the StreamReader one by one, but does not load a line in memory before it's actually needed.
The main point is that this technique allows you to work with huge files while maintaining a small memory usage profile.

With first method (File.ReadAllLines) time elapsed was about 3600 ms. With the second (with extensin method) time elapsed was about 1200 (less than half of first).