Check User Name is Available Or Not Using Asp.net ~ Aspdotnet Studio

Demo:-

Design Code:-

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" EnableEventValidation="false" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Check Username availability Using Ajax</title>
<style type="text/css">
.waitingdiv {
background-color: #F5F8FA;
border: 1px solid #5A768E;
color: #333333;
font-size: 93%;
margin-bottom: 1em;
margin-top: 0.2em;
padding: 8px 12px;
width: 8.4em;
}
</style>

</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="scriptmanager1" runat="server">
</asp:ScriptManager>
<script type="text/javascript">
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
function BeginRequestHandler(sender, args) {
var state = document.getElementById('loadingdiv').style.display;
if (state == 'block') {
document.getElementById('loadingdiv').style.display = 'none';
} else {
document.getElementById('loadingdiv').style.display = 'block';
}
args.get_postBackElement().disabled = true;
}
</script>
<div>

<asp:UpdatePanel ID="PnlUsrDetails" runat="server">
<ContentTemplate>
<table>
<tr>
<td>
UserName:
</td>
<td>
<asp:TextBox ID="txtUsername" runat="server" AutoPostBack="true" ontextchanged="txtUsername_TextChanged"/>
</td>
<td>
<div id="checkusername" runat="server" Visible="false">
<asp:Image ID="imgstatus" runat="server" Width="17px" Height="17px"/>
<asp:Label ID="lblStatus" runat="server"></asp:Label>
</div>
</td>
</tr>
</table>
<div class="waitingdiv" id="loadingdiv" style="display:none; margin-left:5.3em">
<img src="LoadingImage.gif" alt="Loading" />Wait a movment...
</div>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
</body>
</html>

Code Behind:-

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void txtUsername_TextChanged(object sender, EventArgs e)
{
if(!string.IsNullOrEmpty(txtUsername.Text))
{
SqlConnection con = new SqlConnection("Data Source=IT-HP\\sqlexpress;Initial Catalog=Employee;Integrated Security=True");
con.Open();
SqlCommand cmd = new SqlCommand("select * from UserInformation where UserName=@Name", con);
cmd.Parameters.AddWithValue("@Name", txtUsername.Text);
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows)
{
checkusername.Visible = true;
imgstatus.ImageUrl = "NotAvailable.jpg";
lblStatus.Text = "Username is not Available";
System.Threading.Thread.Sleep(2000);
}
else
{
checkusername.Visible = true;
imgstatus.ImageUrl = "Icon_Available.gif";
lblStatus.Text = "UserName Available";
System.Threading.Thread.Sleep(2000);
}}
else
{
checkusername.Visible = false;
}}}