Blogger Tricks

18 May 2012

What is AJAX ?

Ajax is not a stand-alone language or technology. It is a technique that combines a set of known technologies in order to create faster and more user friendly web pages.  It is a client side technology.

AJAX is not a new programming language , but it is a technique for creating better , faster, and more interactive web application.

With AJAx , your Javascript can  communicate directly with the server , using the javascript  XML Http request objects. With this objectsn , your Javascript can trade data with a web server , without reloading the page.

The Ajax technique makes internet application smaller , faster and more user friendly.

>  The XML HTTP Request Object                                          
            By using the XML Http request object, a web developer can update a page with   data from  the server after the page has loaded !

> Scripting with Script manager

The block of code demonstraters the standard way of defining a class in ASP.NET AJAX.  The internals of the client script library are beyond the scope of this article, but in summary the common steps necessary  to creat a class based on the ASP.NET Ajax script extensions are as followes:


  Register the namespace with ASP.NET AJAX
  Create a constructor method
  Create the class proto type by filling in the member methods and their functionality.



For an example, is a consumer of your control was to set a property on an instance of it like this


     Public partial class_Default : system.Web.UI.Page
     {
        Protected void page_load(object sender , WEventArgs e)
        {
             This.MyCustomButton.AlertMessage= “Hey, stop clicking me”!;
        }
    }

 It would be intuitive to also be able to intract with that control instance through script in the browser like this:

<Script type =”text/Javascript ”>
   Function get_text()
  {
    Var mb = $find(“Mycustom button”);
    Var text = mb.get_AlertMessage();
    // do something with the text
  )
</script>

AJAX and ScriptManager

Many developers ,  when first using ASP.NET , starts with the updatePanel control. If a script manager control is included on the page and the updatepanel contains any control, within updetepanel can be asynchronously through the facility of AJAX.

For an example, there is a new and fascinating way to break script references using the UpdatePanel control and AJAX. In days of old you would have added script to the page as a result of a full postback such as this:


Protected void button1_Click (object sender , EventArgs e)

{

   Page.ClientScript.registersatrtupscript(
    This.GetType(), “muscript”,”alert(‘hello world!’);”);

}

But this new method can break under ASP.NET AJAX Why? Because client script manager is not a control that understand partial postbacks and partial rendering, and so script code registered  with it will not be included in the page response for a partial postback.

Instead , if you wanted the button to introduce client script in to the page output , you would leverage the ScriptManager:

Protected void button1_click(object sender, EventArgs e)

{

  scriptManager,registerstartupscript(

     this,this,GetType(),”myscript”,”alert(“hello worls”);”,true);

}

by  Er.Abhijit Pandya
Udaipur City, Rajasthan, India