ASP.Net Label Not Displaying error message text

hi 

I use below code for doesn't insert duplicate data in table 

ALTER procedure [dbo].[insertestate1]
	 @position nvarchar(max)
	,@Transfer nvarchar(20)
	,@Type nvarchar(20)
	,@Behcode nvarchar(10)
	,@Measure varchar(20)
	,@code varchar(20)
	,@id int =0
	,@Success VARCHAR(10) OUTPUT
AS BEGIN
IF NOT EXISTS(SELECT behcode FROM Estate_p WHERE code = @code)
    BEGIN
    INSERT INTO Estate_p
	(
		 position
		,[Type]
		,Transfer
		,Code
		,behcode
	)
	VALUES
	(
		 @position
		,@Type
		,@Transfer
		,@code
		,@Behcode
	)
	SET @Success = 'TRUE'
    END
ELSE
	SET @Success = 'FALSE'
END

Behind code

protected void ImageButton2_Click1(object sender, ImageClickEventArgs e)
    {
        string data = Server.UrlDecode(Request.QueryString["BehCode"]);

      

      
            SqlCommand _cmd = new SqlCommand("insertestate1", _cn);
            _cmd.CommandType = CommandType.StoredProcedure;
            _cn.Open();

         
            _cmd.Parameters.AddWithValue("@Transfer", ddlTran.SelectedItem.Text);
            _cmd.Parameters.AddWithValue("@Type", ddltype.SelectedItem.Text);
            _cmd.Parameters.AddWithValue("@Measure", txtMesure.Text);
   
            _cmd.Parameters.AddWithValue("@Code", Txtcode.Text);
           
            _cmd.Parameters.Add("@Success", SqlDbType.NVarChar,10);
            _cmd.Parameters["@Success"].Direction = ParameterDirection.Output;
      
            _cmd.Parameters.AddWithValue("@id", Convert.ToInt32(ViewState["Id"]));
            int ID = Convert.ToInt32(_cmd.ExecuteScalar());
            if (ID > 0)
            {
                ViewState["Id"] = ID.ToString();
            }
           

            Session["Message"] = true;

            Response.Redirect(Request.Url.AbsoluteUri);
           
            _cn.Close();

            LBLERROR.Text = _cmd.Parameters["@Success"].Value.ToString();

        }

now my problem is that   when it insert or did't insert data in data base it didn't show any message in LBLERROR

Thanks