ASP. NET uses Ajax and jquery to pass parameters back to the foreground and return an instance of the value

1 "Front desk

First, you need a Jquer package.

<script src= "Js/jquery-1.9.1.js" type= "Text/javascript" ></script> below is     <script type= "text/ JavaScript >        $ (function () {            $ (' #txtUserName '). blur (function () {                var username = $ (this). Val ();                $.ajax ({                    type: "Post",                    ContentType: "Application/json",//value-in-A-way                    URL: "Webajaxforme.aspx/getvalueajax", Webajaxforme.aspx is the target file, Getvalueajax is the method data in the target file                    : "{username: '" + Username + "'}",//username                    success:function (Result) {                        alert (RESULT.D),//result.d returned as a background                    }                }) for the background pass parameter (the parameter is optional)            })        })    </script>//here is the source of the parameter        <input id= "txtUserName" type= "text"/>

2 "Backstage

In the background, you first add the using System.Web.Services;

[webmethod]//method must be added in front of [WebMethod] public static string Getvalueajax (string user     Name)//This method needs to be static method to use the keyword static {//here can be passed in the parameters of any operation return username; }