Need to send a id string from client side to server side and fire a event

Take a look at the GetWebRequest, PostWebRequest, and OnWebRequestCompleted JavaScript samples in the AJAX documentation.

Lambert

You can add static page methods to an ASP.NET page and mark them as Web methods. You can then call these methods from script as if they were part of a Web service, but without creating a separate .asmx file. To create Web methods in a page, import the System.Web.Services namespace and add a WebMethodAttribute attribute to each static method that you want to expose. To use the static page methods as Web methods, you must set the EnablePageMethods attribute of the <ScriptManager> to true.

http://ajax.asp.net/docs/tutorials/ExposingWebServicesToAJAXTutorial.aspx