Implementing AJAX in asp.net application using Ajax.dll

Problem: We have a dropdown server control on our web page that we want to populate with users name from the user table in the database when user clicks on the populate button without flickering effect on the web page.

Follow these steps for implementing ajax solution to this problem in your web application using ajax.dll

1. Download the latest version of ajax.dll from the following link:

http://ajax.schwarz-interactive.de/csharpsample/default.aspx

2. Add the httphandler for ajax in the web.config file of your web app.
Example-
< httpHandlers >
< add verb="POST, GET" path="ajax/*.ashx" type="Ajax.PageHandlerFactory, Ajax"/>
< /httpHandlers >

3. Register the aspx.cs class with the ajax.
Exlample-
protected void Page_Load(object sender, EventArgs e)
{

Ajax.Utility.RegisterTypeForAjax(typeof(AjaxDemo));

}

AjaxDemo -is the class name.


4. Now create the serverside ajax method in the .aspx.cs file.
Example-

[Ajax.AjaxMethod]
public DataSet GetUsers()
{
IBLLService ObjBLLService = BLLServiceFactory.GetBLLService();
DataSet Ds=ObjBLLService.GetData();
return Ds;
}
In the GetUsers method, Replace the existing code with your own code to get the users name data from the DB.

5.Write following java script on the .aspx page.

< script language="javascript" type="text/javascript" >

function getusername()
{
AjaxDemo.GetUsers(fillusers);
}
function fillusers(Response)
{
if(Response!=null)
{
var tab=Response.value.Tables[0];
var user=document.getElementById('<%=ddlUsers.ClientID%>');
for(i=0;i < tab.Rows.length;i++)
{
var ro=tab.Rows[i];
user.options[user.options.length]=new Option(ro.firstname,i); // firstname is the field name in the DB table.
}
}
}
< /script >

Add dropdown control and Pupulate button on the web page.

User Name : < asp:DropDownList ID="ddlUsers" runat="server" Width="100%" >

< input id="btnFill" onclick="getusername()" type="button" value="Fill Users using Ajax dll" />

6. We are finished with the coding now its time to test it.