private string ValidateFields()
{
string error = String.Empty;
if (txtUserName.Text.Trim() == String.Empty)
error += "User name is required\n";
if (txtPassword.Text.Trim() == String.Empty)
error += "Password is required\n";
if (txtPassword.Text != txtRePassword.Text)
error += "Passwords do not match\n";
return error;
}