无法从上一页asp.net中检索值

Question

protected void btnAddtoCart_Click(object sender, EventArgs e)
{
        int qty = int.Parse(txtQuantity.Text);
        try
        {
            string connectionStr = ConfigurationManager.ConnectionStrings["AUMSConnectionString"].ConnectionString;
            SqlConnection myConnect = new SqlConnection(connectionStr);
            string command = "INSERT INTO OrderDetails( ProductID, ProductName, UnitPrice, OrderQuantity, UserName) VALUES(@ProductID, @ProductName, @UnitPrice, @OrderQuantity, @UserName)";
            SqlCommand cmd = new SqlCommand(command, myConnect);
            cmd.Parameters.AddWithValue("@ProductID", Convert.ToInt16**(ProductID))**;
            cmd.Parameters.AddWithValue(" @ProductName", name);
            cmd.Parameters.AddWithValue("@UnitPrice", price);
            cmd.Parameters.AddWithValue("@OrderQuantity",qty);
            cmd.Parameters.AddWithValue("@UserName", Session["UserName"].ToString());
            myConnect.Open();
        }
        catch (Exception ex)
        {

        }
}

我无法从上一页检索ProductID，但下面的代码可以使用。

string command = "INSERT INTO OrderDetails(OrderID, OrderBaseID, ProductID, ProductName, UnitPrice, OrderQuantity, AccountID) VALUES(1, 1, "+ Convert.ToInt16(ProductID) + ",'" + name + "','19.00',5,'Lewis')";

谁能告诉我这是什么错误？我试过调试但是返回的值是null。