带有GridView ASP.NET的页面不会显示在浏览器中

Question

我尝试将代码后面的数据绑定到GridView中。我不知道是什么原因导致调试没有错误，但是当我尝试在浏览器中显示页面时它没有显示（孔页面不会出现）

<asp:GridView runat="server" ID="productCart" AutoGenerateColumns="false" EmptyDataText="There is nothing in your shopping cart." GridLines="None" Width="100%" CellPadding="5" ShowFooter="true" DataKeyNames="ProductId">
    <HeaderStyle HorizontalAlign="Left" BackColor="#F36EA7" ForeColor="#FFFFFF" />
    <FooterStyle HorizontalAlign="Right" BackColor="#6C6B66" ForeColor="#FFFFFF" />
    <AlternatingRowStyle BackColor="#F8F8F8" />
    <Columns>
        <asp:BoundField DataField="Description" HeaderText="Description" />
        <asp:TemplateField HeaderText="Quantity">
            <ItemTemplate>
                <asp:TextBox runat="server" ID="txtQuantity" Columns="5" Text='<%# Eval("Quantity") %>'></asp:TextBox><br />
                <asp:LinkButton runat="server" ID="btnRemove" Text="Remove" CommandName="Remove" CommandArgument='<%# Eval("ProductId") %>' style="font-size:12px;"></asp:LinkButton>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="UnitPrice" HeaderText="Price" ItemStyle-HorizontalAlign="Right" HeaderStyle-HorizontalAlign="Right" DataFormatString="{0:C}" />
        <asp:BoundField DataField="TotalPrice" HeaderText="Total" ItemStyle-HorizontalAlign="Right" HeaderStyle-HorizontalAlign="Right" DataFormatString="{0:C}" />
    </Columns>
</asp:GridView>

的.cs：

public partial class Cart : System.Web.UI.Page
{
    UserSingleton activeUser = UserSingleton.Instance;
    List<CartItem_Test> CartItems = null;

protected void Page_Load(object sender, EventArgs e)
{
    DataTable dataTable = Access.GetInfo("CartPerUserID", "*", "UserID=" + activeUser.get_user().ID);
    if (dataTable.Rows.Count > 0)
    {
        CartItems = new List<CartItem_Test>(dataTable.Rows.Count);
        foreach (DataRow row in dataTable.Rows)
        {
            CartItem_Test cartItem = new CartItem_Test(row);
            CartItems.Add(cartItem);
        }
    }

    if (!IsPostBack)
    {
        productCart.DataSource = CartItems;
        productCart.DataBind();
    }
}