无法更新更新页中的数据

我正在通过发送gridview值到其他页面来更新gridview值。在这里，我只能更新类别下拉列表值和图像文件。我无法更新文本框值。

这是我的代码。

更新产品代码:

 protected void SubmitButton_Click(object sender, EventArgs e)
    {
        int productId = Convert.ToInt32(Request.QueryString["ProductID"]);
        Product product = new Product();
        product.ProductID = productId;
        product.ProductName = TitleTextBox.Text;
        product.Description = DescriptionTextBox.Text;
        product.ItemsInSet = Convert.ToInt32(SetTextBox.Text);
        product.UnitPriceOwner = Convert.ToInt32(UnitResellerTextBox.Text);
        product.UnitPriceReseller = Convert.ToInt32(UnitResellerTextBox.Text);
        product.ShippingCost = Convert.ToInt32(ShipmentTextBox.Text);
        product.CategoryID = Convert.ToInt32(CategoryDropDownList.SelectedValue.ToString());
        product.Visible = true;
        product.InOffer = false;
        if (ImageUpload.HasFile)
        {
            int length = ImageUpload.PostedFile.ContentLength;
            product.ProductImage = new byte[length];
            ImageUpload.PostedFile.InputStream.Read(product.ProductImage, 0, length);
        }
        else
        {
            Byte[] image;
            image = ProductBL.GetImage(productId);
            product.ProductImage = image;
        }
        ProductBL.UpdateProduct(product);
        MessageLabel.Text = "Product successfully Updated!";
    }

UpdateProduct()代码:

public static void UpdateProduct(Product product)
    {
        string query = "UPDATE [Products] SET [ProductName] = @ProductName, [Description] = @Description, [ItemsInSet] = @ItemsInSet, " +
                        "[UnitPriceOwner] = @UnitPriceOwner, [UnitPriceReseller] = @UnitPriceReseller, [CategoryID] = @CategoryID, " + 
                        "[ShippingCost] = @ShippingCost, [InOffer] = @InOffer, [ProductImage] = @ProductImage, [Visible] = @Visible WHERE [ProductID] = @ProductID";
        SqlCommand cmd = new SqlCommand(query);
        cmd.Parameters.AddWithValue("@ProductName", SqlDbType.Text).Value = product.ProductName;
        cmd.Parameters.AddWithValue("@Description", SqlDbType.Text).Value = product.Description;
        cmd.Parameters.AddWithValue("@ItemsInSet", SqlDbType.Int).Value = product.ItemsInSet;
        cmd.Parameters.AddWithValue("@UnitPriceOwner", SqlDbType.Int).Value = product.UnitPriceOwner;
        cmd.Parameters.AddWithValue("@UnitPriceReseller", SqlDbType.Int).Value = product.UnitPriceReseller;
        cmd.Parameters.AddWithValue("@CategoryID", SqlDbType.Int).Value = product.CategoryID;
        cmd.Parameters.AddWithValue("@ShippingCost", SqlDbType.Int).Value = product.ShippingCost;
        cmd.Parameters.AddWithValue("@InOffer", SqlDbType.Bit).Value = product.InOffer;
        cmd.Parameters.AddWithValue("@Visible", SqlDbType.Bit).Value = product.Visible;
        cmd.Parameters.AddWithValue("@ProductID", SqlDbType.Text).Value = product.ProductID;
        cmd.Parameters.Add("@ProductImage", SqlDbType.Image).Value = product.ProductImage == null ? (object)DBNull.Value : product.ProductImage;
        DbUtility.UpdateDb(cmd);
    }

页面加载代码:

  protected void Page_Load(object sender, EventArgs e)
    {
        int productId = 0;
        productId = Convert.ToInt32(Request.QueryString["ProductID"]);
        LoadProductDetails(productId);
    }
    protected void LoadProductDetails(int productId)
    {
        var product = ProductBL.GetProductById(productId);
        TitleTextBox.Text = product.ProductName;
        DescriptionTextBox.Text = product.Description;
        SetTextBox.Text = Convert.ToInt32(product.ItemsInSet).ToString();
        UnitOwnerTextBox.Text = Convert.ToInt32(product.UnitPriceOwner).ToString();
        UnitResellerTextBox.Text = Convert.ToInt32(product.UnitPriceReseller).ToString();
        ShipmentTextBox.Text = Convert.ToInt32(product.ShippingCost).ToString();
    }

please Help me

if(!IsPostback)
{
//here
}