如何在 Substitution 控件中使用 ASP.Net 服务器控件? [英] How to use ASP.Net server controls inside of Substitution control?

问题描述

虽然我们在 Substitution 控件中使用的方法应该返回字符串，那么如何使用

while the method we use in Substitution control should return strings, so how is it possible to use a donut caching in web forms on a server control which should be rendered server side?
for example Loginview control?

推荐答案

UPDATE现在这是一个完整的示例.这里发生了一些事情:

UPDATE This is now a fully working example. There a few things happening here:

1. 使用替代控件的回调来呈现您需要的用户控件的输出.
2. 使用覆盖 VerifyRenderingInServerForm 和 EnableEventValidation 的自定义页面类来加载控件，以防止在用户控件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");
}

这里是呈现用户控件的辅助类

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();
    }
}

查看这些相关问题:

• 关闭页面级缓存用户控制
• UserControl 的 RenderControl 是要求在(C#.NET)

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