Gid view is displaying but not getting records from database

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C#

ASP.NET

hi to all,
i'm pretty new to tier architecture model in .net and my problem is
when a username is given in the textbox after clicking the submit button i have to display the grid view when i'm clicking the submit button the grid is displaying but not the values from the database.

here is my code:
DAL:

public DataSet UserDetailGrid(BEL.BEL objBELUserDetailGrid)
        {
            con.Open();
            SqlCommand cmd = new SqlCommand("Usp_GridUserDetails", con);
            cmd.CommandType = CommandType.StoredProcedure;
            try
            {
                DataSet ds = new DataSet();
                cmd.Parameters.AddWithValue("@UserName", objBELUserDetailGrid.UserNam);
                 SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                con.Close();
                return ds;
            }
            catch (Exception ex)
            {
                throw ex;
                return null;
            }
            finally
            {
                cmd.Dispose();
                con.Close();
                con.Dispose();
            }
        }

BLL:

public DataSet UserGridDetail(BEL.BEL objUserDetails)
        {
            DAL.DAL UDGrid = new DAL.DAL();
            DataSet ds = UDGrid.UserDetailGrid(objUserDetails);
            return ds;
        }

InCodeBehind:

protected void BtnDetails_Submit_Click(object sender, EventArgs e)
        {
            Grd_Details.Visible = true;
            BL.BLL objgridviewdetail = new BL.BLL();
            BEL.BEL objGUDBEL = new BEL.BEL();
            objGUDBEL.UserNam = TxtDetails_UserName.Text;

            DataSet ds = objgridviewdetail.UserGridDetail(objGUDBEL);
            Grd_Details.DataSource = ds;
            Grd_Details.DataBind();
        }