如何在Substitution控件中使用ASP.Net服务器控件？

>使用替换控件的回调来呈现所需的usercontrol的输出.
>使用覆盖VerifyRenderingInServerForm和EnableEventValidation的自定义页面类来加载控件,以防止在usercontrol包含需要表单标记或事件验证的服务器控件时引发错误.

这是标记：

<asp:Substitution runat="server" methodname="GetCustomersByCountry" />

这是回调

public string GetCustomersByCountry(string country)
{
   CustomerCollection customers = DataContext.GetCustomersByCountry(country);

    if (customers.Count > 0)
        //RenderView returns the rendered HTML in the context of the callback
        return ViewManager.RenderView("customers.ascx",customers);
    else
        return ViewManager.RenderView("nocustomersfound.ascx");
}

这是用于呈现用户控件的帮助器类

public class ViewManager
{
    private class PageForRenderingUserControl : Page
    {
        public override void VerifyRenderingInServerForm(Control control)
        { /* Do nothing */ }

        public override bool EnableEventValidation
        {
            get { return false; }
            set { /* Do nothing */}
        }
    }

    public static string RenderView(string path,object data)
    {
        PageForRenderingUserControl pageHolder = new PageForUserControlRendering();
        UserControl viewControl = (UserControl) pageHolder.LoadControl(path);

        if (data != null)
        {
            Type viewControlType = viewControl.GetType();
            FieldInfo field = viewControlType.GetField("Data");
            if (field != null)
            {
                field.SetValue(viewControl,data);
            }
            else
            {
                throw new Exception("ViewFile: " + path + "has no data property");
            }
        }

        pageHolder.Controls.Add(viewControl);
        StringWriter result = new StringWriter();
        HttpContext.Current.Server.Execute(pageHolder,result,false);
        return result.ToString();
    }
}

请参阅以下相关问题：

> Turn off page-level caching in a
user control
> UserControl’s RenderControl is asking for a form tag in (C# .NET)