private bool CheckInput()
 {
     if (string.IsNullOrEmpty(TxtUserName.Text.Trim()) || string.IsNullOrEmpty(TxtPassword.Text.Trim()) ||
         string.CompareOrdinal(TxtUserName.ToString(), TxtUserName.Text.Trim()) == 0 ||
         string.CompareOrdinal(TxtPassword.ToString(), TxtPassword.Text.Trim()) == 0)
     {
         LblErrorMessage.Content = "User name or password error.";
         return(false);
     }
     return(true);
 }