我试图通过page方法返回用户/服务器控件的html表示。当我调用采用用户控件的虚拟路径的重载时，它起作用，但当我尝试调用采用类型的重载时，它不起作用。示例代码如下。有什么建议吗？

[WebMethod]
public static string LoadAlternates(string productId, string pnlId)
{
    object[] parameters = new object[] { pnlId, productId };
    return ControlAsString(typeof(PopupControl), parameters);
}

private static string ControlAsString(Type controlType, object[] parameters)
{
    Page page = new Page();
    UserControl controlToLoad;
    /*
     *calling load control with the type results in the 
     *stringwriter returning an empty string
    */

    controlToLoad = page.LoadControl(controlType, parameters) as UserControl;
    /*
     *However, calling LoadControl with the following overload
     *gives the correct result, ie the string rep. of the control.
    */
     controlToLoad = page.LoadControl(@"~/RepeaterSamples/PopupControl.ascx") as UserControl;

    //some more code, then this... 
    page.Controls.Add(controlToLoad);

    StringWriter sw = new StringWriter();
    HttpContext.Current.Server.Execute(page, sw, false);
    return sw.ToString();
}

你知道为什么StringWriter会返回一个空字符串吗？我应该指出的是，所有的“页面”生命周期都正确执行，而不管选择什么方法来调用LoadControl。
想要添加-我必须使用LoadControl(Type, object[])重载。：—（