Availability of name in login page in csharp

In this blog we can Verify Availability of name in database.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<title>Untitled Page</title>

</head>

<body>

<div>

</div>

<asp:Button ID="Button1" runat="server" Text="Availability of name from the database"

BackColor="#FF99FF" Font-Bold="True" Width="329px"

onclick="Button1_Click" /><br />

<asp:Label ID="Labelcheck" Text="Please enter any name to be verified from the database" runat="server" BackColor="#FFFF99"

Width="197px" ForeColor="#FF3300"></asp:Label>

<asp:TextBox ID="txtUserName" runat="server" Width="197px"></asp:TextBox>

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"

ControlToValidate="txtUserName" ErrorMessage="*Name Required"></asp:RequiredFieldValidator>

<br />

<asp:Label ID="lblMessage" runat="server" BackColor="#FF3300"

ForeColor="Black"></asp:Label>

</form>

</body>

</html>

using System;

using System.Configuration;

using System.Data;

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;

using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page

{

string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

SqlCommand com ;

string str = null;

protected void Button1_Click(object sender, EventArgs e)

{

namecheck();

}

public void namecheck()

{

SqlConnection con = new SqlConnection(connStr);

con.Open();

str = "select count(*)from employee where ename='" + txtUserName.Text + "'";

com = new SqlCommand(str, con);

int count = Convert.ToInt32(com.ExecuteScalar());

if (count > 0)

{

lblMessage.Text = "Sorry! you can't take this username";

}

else

{

lblMessage.Text = "You can take this username";

}