. NET generic handler to implement user name validation

JS section:
<script type= "Text/javascript" >
Verify that the user name is correct
function Judgeusername () {
var username = $ ("#userName"). Val ()
$.ajax ({
Type: "Post",
URL: ' registerusernameverity.ashx/processrequest?username= ' +username,
Success:function (Result) {
if (username = = "") {
Alert ("User name cannot be empty!") ");
document.getElementById ("UserName"). focus ();
document.getElementById ("UserName"). Selected;
} else {
if (result = = "True") {
Alert ("already exists, please re-select a user name!") ")
document.getElementById ("UserName"). Focus;
document.getElementById ("UserName"). Select ();
}
}
},
});
}
</script>

HTML section:
<input type= "text" onblur= "Judgeusername ()"/>

General Handler section:
public void ProcessRequest (HttpContext context)
{
Get it from the front desk.
String userName = context. Server.urldecode (context. request.querystring["username"]);
Declares an object that queries whether a user name exists
USERBLL VERIFYUSERNAMEBLL = new USERBLL ();
To judge by other functions.
BOOL FLAG=VERIFYUSERNAMEBLL. Exists (UserName);
if (flag==true)
{
Context. Response.Write (True);
}
Else
{
Context. Response.Write (FALSE);
}
}

. NET generic handler to implement user name validation