Ajax Asynchronous postback

Introduction 

Ajax helps the users to send and receive value from server asynchronously.

Background 

Using ajax we can send and receive data from server with our reloading the page(postback).  So the page will nor refresh if a server call encounters.

Using the code

A jquery library should be added to avail this ajax functionality to the page.

<script src="Scripts/jquery-1.4.1.min.js" type="text/javascript"></script>

Then we can use $.ajax({}); method in our page script.

syntax for this function

$.ajax({name:value, name:value, ... }) 

The ajax() method is used to perform an AJAX (asynchronous HTTP) request.

All jQuery AJAX methods use the ajax() method. This method is mostly used for requests where the other methods cannot be used.

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usually this method would be like this.

$.ajax({
                   type: "POST",
                   url: "sample.aspx/ShowValue",
                   data: "{'data':'myname','value1':'123456a'}",
                   contentType: "application/json; charset=utf-8",
                   dataType: "json",
                   async: true,
                   success: function (msg) {
                       suc(msg);
                   },
                   error: function (msg) {
                       alert(msg.responseText);
                   }

               });

url: "sample.aspx/ShowValue"  specifies the page name and the function name.

[WebMethod]
public static string ShowValue(string data, int value1)
{
    return DateTime.Now.ToString() + " " + data + " " + value1;
}

data: "{'data':'myname','value1':'123456a'}" 

The parameters passed to the code behind as a json object.

A JSONObject is an unordered collection of name/value pairs. Its external form is a string wrapped in curly braces with colons between the names and values, and commas between the values and names. The internal form is an object having get and opt methods for accessing the values by name, and put methods for adding or replacing values by name. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, String, or the JSONObject.NULL object.

myString = new JSONObject().put("JSON", "Hello, World!").toString();

produces the string {"JSON": "Hello, World"}.

the following blog post contains 5 postback in a single button click without user awareness.

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