AsyncFileUpload动态添加自定义控件

Question

创建一个具有异步文件上载控件的自定义控件。但是，当我尝试在控件中添加异步FileUpload时，无法添加获取补时错误。以下是我的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using AjaxControlToolkit;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace SBITS.CustomControl
{
class CustomFileUpload:CompositeControl
{

    private AsyncFileUpload asyncFileUpload;

    private Image throbberImage;


    protected override void CreateChildControls()
    {

        this.throbberImage = new Image();
        this.throbberImage.ImageUrl = Constant.THROBBER_IMAGE_PATH;
        this.Controls.Add(throbberImage);

        this.asyncFileUpload = new AsyncFileUpload();
        this.asyncFileUpload.ThrobberID = throbberImage.ID;
        this.Controls.Add(asyncFileUpload);
    }
}  }

在这条线上得到错误

 this.Controls.Add(asyncFileUpload);

误差屏

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编译时间误差

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Answer 1

得到了该问题的解决方案，将system.web.Extension的参考加入到我的项目中，并完成了。