无法修改Controls集合，因为该控件包含代码块(即<%…%>)动态添加具有母版页的控件

不能修改控件集合，因为当动态添加具有母版页的控件时，控件包含代码块(即<%…%>)

我正在尝试添加一个隐藏字段控件到aspx页面。我得到下面提到的错误

无法修改Controls集合，因为该控件包含代码块(即<%…%>)。

当我必须动态添加控件时，就会发生这种情况。在网上，我找到了所有类型的答案，用<%#代替<%=。在我的情况下，这根本不适用。

 HiddenField hndGuid = new HiddenField();
_page.Form.Controls.Add(hndGuid);

指针吗?

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Collections.Generic;
namespace wwwroot.Common
{
    public class GuidClass
    {
        public GuidClass()
        {
            //
            // TODO: Add constructor logic here
            //
        }
        private string guid;
        public string Guid
        {
            get
            {
                return guid;
            }
            set
            {
                guid = value;
            }
        }
    }
    public class Myhandler : System.Web.UI.Page, IHttpModule
    {
        Page _page = null;
        HiddenField hndGuid = null;
    Queue<string> temp;
    public Myhandler()
    {
        temp=new Queue<string>();
    }
    public new void Init(HttpApplication context)
    {
        context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute);
    }

    void context_PreRequestHandlerExecute(object sender, EventArgs e)
    {
        System.Web.HttpContext _httpContext = System.Web.HttpContext.Current;

        if (_httpContext != null)
        {
            _page = _httpContext.Handler as System.Web.UI.Page;
            if (_page != null)
            {
                _page.Init += new EventHandler(_page_Init);
                _page.Load += new EventHandler(_page_Load);
                hndGuid = new HiddenField();
                hndGuid.ID = "hndGuid";
            }
            else
            {
                return;
            }
        }
        else
        {
            return;
        }
    }
    void _page_Init(object sender, EventArgs e)
    {
        _page.Form.Controls.Add(hndGuid);
        if (!_page.IsPostBack)
            hndGuid.Value = Guid.NewGuid().ToString();
    }
    void _page_Load(object sender, EventArgs e)
    {
        GuidClass currentGuid =new GuidClass();
        currentGuid.Guid = hndGuid.Value;
        System.Web.HttpContext _httpContext = System.Web.HttpContext.Current;
        if (temp.Contains<string>(currentGuid.Guid))
        {
            _httpContext.Items.Add("IsRefresh",true);
        }
        else
        {
            if(!(currentGuid.Guid.Equals(null)||currentGuid.Guid.Equals("")))
                temp.Enqueue(currentGuid.Guid);
            _httpContext.Items.Add("IsRefresh",false);
        }
    }
    }
}