[Solved] ASP.Net Update command not updating record in database

This codes works like this, you select the desired data from the dropdown, then it auto post back and displays it on the textbox brand, then change the data displayed on textbox and update.

So everything is selecting but when you change your data displayed on textbox and click update nothing updates, i don’t know why?

See all codes 

            if (!this.IsPostBack)
            {
                string Constr1 = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
                using (SqlConnection CONE = new SqlConnection(Constr1))
                {
                    using (SqlCommand C0MDE = new SqlCommand("SELECT C_ID,Brand FROM Brands "))
                    {
                        C0MDE.Parameters.AddWithValue("@Brand", this.ddljob.SelectedValue.Trim());

                        // C0MDE.Parameters.AddWithValue("@UserName", Session["userName"]);
                        C0MDE.CommandType = CommandType.Text;
                        C0MDE.Connection = CONE;
                        CONE.Open();
                        ddljob.DataSource = C0MDE.ExecuteReader();
                        ddljob.DataValueField = "C_ID";
                        ddljob.DataTextField = "Brand";
                        // ddlProductCode.DataValueField = "UserName";

                        ddljob.DataBind();
                        CONE.Close();
                    }
                }
                ddljob.Items.Insert(0, new ListItem("--Select Job ID--", "0"));
            }
        }

        protected void ddljob_SelectedIndexChanged(object sender, EventArgs e)
        {
            string constr = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                SqlCommand command = new SqlCommand("SELECT Brand FROM Brands WHERE Brand = @Brand", con);
                command.Parameters.AddWithValue("@Brand", ddljob.SelectedItem.Text);
                con.Open();
                SqlDataReader sdr = command.ExecuteReader();
                if (sdr.Read())
                {
                    txtprebrand.Text = sdr["Brand"].ToString();
                    // txtsub.Text = sdr["SubCategory"].ToString();
                    // txtprice.Text = sdr["Price"].ToString();
                    // txtdiscount.Text = sdr["Discount"].ToString();
                }
                sdr.Close();
            }
        }

        protected void btnitems_Click(object sender, EventArgs e)
        {
            String strConnString = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection conn4 = new SqlConnection(strConnString);
            SqlCommand cmdD = new SqlCommand();
            cmdD.CommandType = CommandType.Text;
            cmdD.CommandText = "UPDATE Brands SET Brand = @Brand WHERE Brand= @Brand";

            //  cmdD.Parameters.AddWithValue("@C_ID", ddljob.SelectedItem.Text.Trim());
            cmdD.Parameters.AddWithValue("@Brand", txtprebrand.Text.Trim());
            // cmdD.Parameters.AddWithValue("@SubCategory", txtsub.Text.Trim());
            //  cmdD.Parameters.AddWithValue("@Price", txtprice.Text.Trim());
            // cmdD.Parameters.AddWithValue("@Discount", txtdiscount.Text.Trim());
            //   cmdD.Parameters.AddWithValue("@UserName", HttpContext.Current.User.Identity.Name);
            cmdD.Connection = conn4;
            try
            {
                conn4.Open();
                tbljobs.EmptyDataText = "No Records Found";
                tbljobs.DataSource = cmdD.ExecuteReader();
                tbljobs.DataBind();
                ScriptManager.RegisterClientScriptBlock(btnitems, this.GetType(), "alert", "<script>alert('Data Updated Successfully ... !!')</script>", false);
                // lblMessage2.Text = "Inserted Quantity Is Higher than  stock " + GetQuantity().ToString();

            }
            catch (Exception ex)
            {
                throw ex;
            }//
            finally
            {
                conn4.Close();
                conn4.Dispose();
            }
        }