Telerik RadWindow不会打开代码

Question

我正在尝试从我的代码后面打开一个radwindow，而不是使用javascript。但我无法弄清楚我做错了什么。

RadWindow Manager

<telerik:RadWindowManager ID="RadWindowManager1" runat="server" EnableShadow="true">

</telerik:RadWindowManager>

控制打开radwindow

<asp:Button runat="server" ID="PortChatButton" Text="Questions?" OnClick="PortChatClick" />

背后的代码

protected void PortChatClick(object sender, EventArgs e)
{
    RadWindow portChat = new RadWindow();
    portChat.Modal = true;
    portChat.ID = "PortingChatModal";
    portChat.NavigateUrl = "~/PortingChat.aspx";
    portChat.Style["z-index"] = "9999";
    portChat.AutoSize = true;
    portChat.VisibleTitlebar = false;
    portChat.VisibleStatusbar = false;
    portChat.Visible = true;
    RadWindowManager1.Windows.Add(portChat);
    portChat.Visible = true;
    return;
}

我不明白为什么这样做不起作用。