Incremental Page Display Pattern for User Controls

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Web.UI;
using System.Web;
using System.Web.UI.HtmlControls;

namespace ControlLoading
{
    internal class IncrementalLoaderHandler : IHttpHandler
    {
        private StringBuilder _controlBuilder;
        private StringWriter _controlWriter;
        private HtmlTextWriter _htmlWriter;

        #region IHttpHandler Members
        /// <summary>
        /// Accepts incoming HTTP requests and executes the resource specified in the querystring
        /// </summary>
        /// <param name="context">An <see cref="T:System.Web.HttpContext"></see> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) used to service HTTP requests.</param>
        public void ProcessRequest(HttpContext context)
        {
            // *** Simulate latency ***
            Random r = new Random();
            int wait = r.Next(500, 3000);
            System.Threading.Thread.Sleep(wait);

            if (context.Request.QueryString[IncrementalLoader.ControlQuery] != null)
            {
                try
                {
                    // Create a page instance to host the user control
                    Page page = new Page();

                    // ** Alternative for rendering controls that need a <form> tag
                    //HtmlForm form = new HtmlForm();

                    string controlLocation = Utility.DecryptString(context.Request.QueryString[IncrementalLoader.ControlQuery]);
                    UserControl control = (UserControl)page.LoadControl(controlLocation);

                    page.Controls.Add(control);

                    // ** Alternative for rendering controls that need a <form> tag
                    //page.Controls.Add(form);
                    //form.Controls.Add(control);
                    //form.SetRenderMethodDelegate(new RenderMethod(RenderForm));

                    // Execute the page and return the output (only the control's output is returned)
                    StringWriter output = new StringWriter();
                    context.Server.Execute(page, output, false);

                    // ** Alternative for rendering controls that need a <form> tag
                    //((IHttpHandler)page).ProcessRequest(context);

                    context.Response.Clear();

                    context.Response.Write(output.ToString());
                    
                    // ** Alternative for rendering controls that need a <form> tag
                    //context.Response.Write(_controlWriter.ToString());
                }
                catch { }
            }
        }
        /// <summary>
        /// Renders the control.
        /// </summary>
        /// <param name="hw">The hw.</param>
        /// <param name="ctrl">The CTRL.</param>
        protected void RenderForm(HtmlTextWriter writer, Control control)
        {
            _controlBuilder = new StringBuilder();
            _controlWriter = new StringWriter(_controlBuilder);
            _htmlWriter = new HtmlTextWriter(_controlWriter);

            foreach (Control child in control.Controls)
            {
                if (!(child is ScriptManager))
                {
                    child.RenderControl(_htmlWriter);
                }
            }
        }
        /// <summary>
        /// Gets a value indicating whether another request can use the <see cref="T:System.Web.IHttpHandler"></see> instance.
        /// </summary>
        /// <value></value>
        /// <returns>true if the <see cref="T:System.Web.IHttpHandler"></see> instance is reusable; otherwise, false.</returns>
        public bool IsReusable
        {
            get { return true; }
        }
        #endregion
    }
}