I got this exception when I tried to run my Repository tests and couldn’t find the exact reason why these tests failed.

All the unit tests where passing before I removed the default constructors from Domain Model, when I reverted the default constructors back, everything started working again….. !!!

Do you know the exact reason for this?

Update: In order to support lazy loading, NHibernate needs to create proxy objects. Those proxy classes derived from the actual domain model class itself, and they are instantiated using the default constructor. So the parent class also should have a default constructor.

Have you ever thought about how chatting in Gmail works? I think it works using a programming technique called Comet.

What is comet programming

In web development, Comet is a neologism to describe a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term for multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins

Last few days, I was reading about this technology and thought about sharing the information with you all. Please find the attached sample application which demonstrates how comet works using Asp.Net (Note: Right now it works only in firefox. Fixes or patches to make it work in IE/Safari.. or all the browsers in this world are welcome J )

Please download the demo from here

If you have method, which does the string reverse. So normally we writes test cases in Nunit something like this

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[Test]
public void TestCase1()
{
  ExString exString = new ExString();
  Assert.AreEqual("dcba", exString.Reverse("abcd"));
}

[Test]
public void TestCase2()
{
  ExString exString = new ExString();
  Assert.AreEqual("abba", exString.Reverse("abba"));
}

This means, you are repeating the same code again and again in order to test different possibilities. The down side of this approach is, in long run it will be very difficult to manage the test case when compared to the actual code.

To solve this particular problem NUnit has got parameterised test cases attribute, so the same could be re write above test case to

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[TestCase("abcd", "dcba", TestName = "Test Case 1")]
[TestCase("abcd1", "1dcba", TestName = "Test Case 2")]
[TestCase("aaaa", "aaaa", TestName = "Test Case 3")]
[TestCase("abba", "abba", TestName = "Test Case 4")]
public void Can_Reverse_A_Text(string actual, string expected)
{
  ExString exString = new ExString();
  Assert.AreEqual(expected, exString.Reverse(actual));
}

This gives a clean way for testing different possibilities, all these shown in the NUnit test runner as different test cases like below.

Hope this will help in some way or other

Here I wanted to show you the flexibility of JQuery. Below is a HTML code that generates a grid with two rows and ten columns.

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<div id="container">
    <div class="column">1</div>
    <div class="column">2</div>
    <div class="column">3</div>
    <div class="column">4</div>
    <div class="column">5</div>
    <div class="column">6</div>
    <div class="column">7</div>
    <div class="column">8</div>
    <div class="column">9</div>
    <div class="column">10</div>
</div>

When the user double clicks on any of the cell, he can edit that content. The cell value get updated when user double clicks on any other cell.

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$(document).ready(function() {
    $("#container .column").dblclick(function() {

        var content = $(this).text();
        var width = $(this).width() - 1;
        var height = $(this).height() - 4;

        var $editbox = $("<input type='text'" +
            "style='width:" + width + ";" +
            "height:" + height + ";" +
            "border:none" +
            "' value='" + content + "' />");

        $(this).empty();
        $(this).prepend($editbox);
        $editbox.focus();
        $editbox.select();

        $($editbox).bind("blur", function() {

            content = $(this).val();
            var parent = $(this).parent();
            parent.html(content);

        });

    });
});

The above code does all the trick. First we hook the Double Click event to all the DIV with class name column using this $("#container .column").dblclick(function(){...}); Inside that, we dynamically add a textbox inside the DIV and set its text value as the HTML content of the parent DIV. And also we bind the blur event of this texbox to a function, so that whenever the focus leaves from the textbox, that function is called. Then inside that function, we set the HTML content of the DIV with the Textbox value.

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$($editbox).bind("blur", function() {
     content = $(this).val();
     var parent = $(this).parent();
     parent.html(content);

 });

See the working demo below

Recently I read about Text Template Transformation Toolkit(T4), I was really amazed by this because I thought only CodeDOM was the only way to generate code.

T4 is a template based code generation engine which comes with Visual Studio 2008 (It is not a framework feature).

This simple example shows how powerful it is -

if you have a string array and you want to generate a strongly typed enum from this.

###Steps

1) Open up VS 2008 and Create a project.
2) Add a file called “EnumGenerator.tt” to the project. Accept the warning when add this file. Paste these code into the file you have created right now.

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<#@ template language="C#" hostspecific="True" debug="True" #>
<#@ output extension="cs" #>
<#
  string[] values = new string[]{"Red","Green","Blue"};
#>

namespace TextTemplate {
<#
  PushIndent("\t");
#>
enum Color {
  <#
    for(int i = 0; i < values.Length; i++)
    {
      PushIndent("\t");
      WriteLine(values[i] + ((i != values.Length -1) ? "," : ""));
      PopIndent();
    }
  #>
}
<#
  PopIndent();
#>

3) Done! Click the plus sign near the EnumGenerator.tt, you can see the source code.

The beauty of this technique is, it is not runtime or compile time. The code is generated at design time which allow you to use this enum(or whatever code you have generated) at the same time you write your code.

To learn more about this, here is the great link - http://www.olegsych.com/2007/12/text-template-transformation-toolkit/

You want to create simple GUI cross platform application without knowing the high level programming languages like C++, Java, C#~(using mono)? XUL is that answer.

Yes it is possible using XUL, the prerequisites for this is, knowledge of a declarative programming language(like HTML or XHTML, XAML etc…) and JavaScript.

XUL is basic building block of the Firefox UI and as we know Firefox works in Windows, Linux and MAC.

Actually XUL is a language which run on the XULRunner(Gecko) runtime from Mozilla.

If you really wants see how Firefox created this UI, go the FireFox installation folder. Normally it will be C:\Program Files\Mozilla Firefox\. Under that installation root folder, find a folder named “chrome”. Firefox has packaged the xul files in a zip format and they have renamed it as .jar. So look for a file browser.jar and rename it to zip. Extract it and have a look at content\browser\browser.xul. This file holds the UI definition for Firefox.

To learn more about XUL, refer these web sites

1. http://www.mozilla.org/projects/xul/
2. http://www.ibm.com/developerworks/web/library/wa-xul1/

Part 1 - Calling Server Side methods from Client Side

In this post, I will explain how to pass data from client to server in JSON format.

Microsoft AJAX client library has built-in methods which helps in serializing and de-serializing JSON. The methods are defined in Sys.Serialization.JavaScriptSerializer class. In server side we have JavaScriptSerializer that will help you out to do the JSON serialization and de-serialization.

With the help of these two classes, we can easily do the data transfer. Suppose you have class called Customer in server side, which looks like this

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namespace ServerClientInteration
{
    [Serializable]
    public class Customer
    {
        public int ID { get; set; }

        public string Name { get; set; }

        public string Address { get; set; }
    }
}

This is our payload for this example, we are going to move this object from server to client and vice versa. For that I have exposed two static methods on the server side; one is for retrieving the customer details and the other is for updating the customer.

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public partial class _Default : System.Web.UI.Page
  {
      private static Customer customer = null;

      protected void Page_Load(object sender, EventArgs e)
      {
          if (customer == null)
          {
              customer = new Customer();
              customer.ID = 1;
              customer.Name = "microsoft";
              customer.Address = "www.microsoft.com";
          }

      }

      [WebMethod]
      [ScriptMethod(UseHttpGet=true)]
      public static string GetTime()
      {
          return DateTime.Now.ToLongTimeString();
      }

      [WebMethod]
      [ScriptMethod(UseHttpGet = true)]
      public static string GetCustomer()
      {
          JavaScriptSerializer serializer = new JavaScriptSerializer();
          return serializer.Serialize(customer);
      }

      [WebMethod]
      [ScriptMethod]
      public static string UpdateCustomer(string jsonCustomer)
      {
          try
          {
              JavaScriptSerializer serializer = new JavaScriptSerializer();
              Customer cust = serializer.Deserialize(jsonCustomer);
              customer.ID = cust.ID;
              customer.Name = cust.Name;
              customer.Address = cust.Address;

              return "Updated";
          }
          catch(Exception Exception)
          {

          }

          return "Error occured while updating";
      }
  }

In the above code, you can see GetCustomer and UpdateCustomer methods. GetCustomer will serialize the static customer object and return it as JSON string; UpdateCustomer method accepts JSON string as input and that string is de-serialized in to a customer object and the static customer variable is updated with the new values. UpdateCustomer will return status message after the update.

Usually, we persist the customer in DB or some other states, but here for simplicity I have used a static variable which will simulate the persistence.

Now we need to call this from the client-side, for that I have two hyperlinks; one will get the customer from the server and other send the customer to the server.

Here is how the HTML looks like

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<head runat="server">
  <title>Untitled Page</title>
  <style type="text/css">  
    #result
    {
      width: 250px;
      height: 300px;
      overflow: auto;
      border:1px solid #00d;
    }
  </style>
</head>
<body>
  <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true">
    </asp:ScriptManager>
    <div>
        <a href="javascript:callServerMethod()" >Call Server method</a>
        <hr />
        <a href="javascript:getCustomer()" >Get Customer</a>
        <div id="result"></div>
        <hr />
        <div>
          ID : <input type="text" id="custID" /><br />
          Name : <input type="text" id="custName" /><br />
          Adress : <input type="text" id="custAdd" /><br />
        </div>
        <a href="javascript:updateCustomer()" >Update customer</a><br />
    </div>

    <script language="javascript" type="text/javascript">
      //<![CDATA[
      function callServerMethod() {
        PageMethods.GetTime(callBackMethod);
      }

      function callBackMethod(result) {
        alert(result);
      }

      function getCustomer() {
        PageMethods.GetCustomer(callBackGetCustomer);
      }

      function callBackGetCustomer(result) {
        var customer = Sys.Serialization.JavaScriptSerializer.deserialize(result);
        var content = "<br />ID :" +  customer.ID + "<br />" + "Name : " + customer.Name + "<br />" + "Address : " + customer.Address;
        $get("result").innerHTML += content;
      }

      var clientCustomer = function(id,name,add){
        this.ID = id;
        this.Name = name;
        this.Address = add;
      };


      function updateCustomer() {
        var id = $get("custID").value;
        var name = $get("custName").value;
        var address = $get("custAdd").value;

        var customer = new clientCustomer(id,name,address);
        var serializedCustomer = Sys.Serialization.JavaScriptSerializer.serialize(customer);
        PageMethods.UpdateCustomer(serializedCustomer,callBackUpdateCustomer);
      }

      function callBackUpdateCustomer(result) {
        alert(result);
      }

      //]]>
    </script>
  </form>
</body>

I think the above code is self explanatory, let me know if you have any difficulty in understanding this. Hope this will gave some idea about passing JSON between client and server.

I have uploaded the source code in my server and you can get it from here - //static.rajeeshcv.com/download/ServerClientInteration.zip

Part2 - ASP.NET AJAX - Passing JSON Object from Client to Server

ASP.net AJAX has got nice bridging between your server side and client side technologies. Using the ASP.net AJAX you can easily call a method in a page. The restriction here is that, the methods your are trying to call should be static and public.

This feature(calling server side static method) is not enabled by default, so you have to manually enable this and it is very very simple; just set the EnablePageMethods property of the ScriptManager to true like this

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<asp:scriptmanager id="ScriptManager1" runat="server" enablepagemethods="true"></asp:scriptmanager>

After this, create a public static method in your asp.net page and decorate it with WebMethod(System.Web.Services.dll) and ScriptMethod(System.Web.Extensions.dll) attributes. For example I have created a static method called GetTime() which returns current time as string.

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public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    [WebMethod]
    [ScriptMethod]
    public static string GetTime()
    {
        return DateTime.Now.ToLongTimeString();
    }
}

Now you have configured everything correctly and I will show you how to call this method from the client side.

Earlier you have set the EnablePageMethods property of ScriptManager to true, as a result of that a new object called PageMethods is created by the ScriptManager when the page is rendered. This object has all the public static methods in that page. So that you call the server side method like PageMethods.[ServerSideMethodName]. When calling this methods from client side you have to provide a callback function because here all the call scriptmanager made will be asynchronous, and this callback method will get the returned result.

Below is the sample code

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<form id="form1" runat="server">
  <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true">
  </asp:ScriptManager>
  <div>
    <a href="javascript:callServerMethod()" >Call Server method</a>
  </div>
  <script language="javascript" type="text/javascript">
  //<![CDATA[function callServerMethod() {
            PageMethods.GetTime(callBackMethod);
          }
          function callBackMethod(result) {
            alert(result);
          }
  //]]>
  </script>
</form>

###Extra bits
In the above code you can see that I have placed link, when user click on that link a message is shown with the server time. So behind an asynchronous request is send to the server in this format http://[sitename]/[MethodName]. Server in turn returns the result as JSON back to the client. Here is a screen shot from the firebug

There is an optimization we have do here - you can see that, by default the request is a POST request, but in our case a POST request is heavy because we could have achieved the same using a GET request (Difference between POST and GET).

In order to change this request in to a GET request, we need to do a minor tweaking in the server side, set UseHttpGet=true parameter for the ScriptMethod attribute.

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[WebMethod]
[ScriptMethod(UseHttpGet=true)]
public static string GetTime()
{
    return DateTime.Now.ToLongTimeString();
}

After this you can see that, request is changed to a GET request

Silverlight 2 is out now with new features like rich set of controls, improved Text Rendering capabilities, rich networking support including calling secured(SSL) services etc…

Moreover Microsoft is partnered with Soyatec to sponsor tools for developing Silverlight applications using cross platform Eclipse development platform. eclipse2SL is first of that kind.

eclipse2SL is an open source tools integrated with the Eclipse development platform that enable Java developers to use the Eclipse platform to create applications that run on the Microsoft Silverlight runtime platform. Specifically, the project will be an Eclipse plug-in that works with the Eclipse Integrated Development Environment (IDE) and Eclipse Rich Client Platform (RCP) to provide both a Silverlight development environment and greater interoperability between Silverlight and Java, to facilitate the integration of Silverlight-based applications into Java-based web sites and services.

As an addition to the control set Microsoft is releasing Silverlight Toolkit by end of this month with more UI controls.

Silverlight 2 resources

To get the basic understanding go to Get started, here are some good articles written by Scott Guthrie

1. Introduction
2. Creating “Hello World” with Silverlight 2 and VS 2008
3. Using Layout Management
4. Using Networking to Retrieve Data and Populate a DataGrid
5. Using Style Elements to Better Encapsulate Look and Feel
6. Using the ListBox and DataBinding to Display List Data
7. Using User Controls to Implement Master/Details Scenarios
8. Using Templates to Customize Control Look and Feel
9. Creating a Digg Desktop Version of our Application using WPF

Google chrome(0.2.149.30) has got some problem in rendering the checkboxes. Today I thought about buying a new laptop, so I was searching for a laptop that will fit into my budget and requirements. And I came across a website called http://www.compareindia.com/products/laptops/ , I was using Google chrome for browsing, but when viewed that page it was like this

There was no way for me to narrow my search because I couldn’t select any of options listed under “Narrow your Search” section, but after sometime i.e after doing some scrolling and switching tabs checkboxes appeared on the left side of this list

Initially I thought that, it will a problem with the way that page was developed(may be some JavaScript issues), but when I opened the same page in Firefox(3.0.1) it was rendering properly, even in IE 6 is rendered that page correctly.

FF I think this is a Chrome bug; I have reported this , follow this URL http://code.google.com/p/chromium/issues/detail?id=3151 if you have experienced same problem.