Try this code:
protected void Username_Changed(object sender, EventArgs e)
{
SqlConnection conn = new SqlConnection(”Server=Database; Initial Catalog=achu; Integrated Security=SSPI”);
SqlCommand cmd = new SqlCommand(“select * from aspnet_Users”,conn);
conn.Open();
SqlDataReader dr;
System.Threading.Thread.Sleep(3000);
dr = cmd.ExecuteReader();
while (dr.Read())
{
if (TextBox1.Text == dr["UserName"].ToString())
Label1.Text=”Username already exists”;
else
Label1.Text = “Username available “;
}
or try this code :
protected void Username_Changed(object sender, EventArgs e)
{
if(Membership.GetUser(Username.Text) != null)
{
Label1.Text=”Username already exists”;
}
else
{
Label1.Text = “Username available “;
}
Good Luck
