MVC模式下如何实现RegisterStartupScript等功能

本文源于http://www.achtmaal.com/blog/asp-net-mvc-and-registerclientscriptinclude，非常感谢原文作者的智慧和分享

RegisterStartupScript系列的向前台输出脚本的方法，是基于WebForm的，在MVC日益盛行的时代，它则无法正常工作了。但不论出于什么原因，也许你还会需要用到它，至少我有这样的需求。原文的作者提供了一个方法，我这里不作翻译，简单地描述一下工作原理。

1. 每一个页面虽然不再是Page对象，用不了Register***功能，但是它仍然在一个HTTP Pipeline里面。
2. 每一个页面请求的HttpContext.Current.Items仍然适用，它对每一个请求负责，我们将不同的Script存在里面，并在Http Pipeline的不同EventHandler中进行处理。
3. HttpContext.Current.Reponse.Filter可以截获整个页面的流，可以将其中的内容进行改写。

与原文不同，我的代码场景和他不同，所以我做了简化。

1. HtmlScriptHelper提供给用户进行调用，目的是向HttpContext.Current.Items中添加Script，调用方法和以前一样。

2. 在context.BeginRequest += Context_BeginRequest;处理程序中，向HttpContext.Current.Reponse.Filter中添加过滤器。

 public class HtmlScriptStream : MemoryStream
     {
         private Stream OutputStream { get; set; }
         private HttpContext HttpContext { get; set; }
         private bool closing;

         public HtmlScriptStream(Stream outputStream, HttpContext httpContext)
         {
             this.OutputStream = outputStream;
             this.HttpContext = httpContext;
         }

         public override void Close()
         {
             // Using a StreamReader to read this will cause Close to be called again
             if (this.closing)
             {
                 return;
             }

             this.closing = true;
             byte[] buffer = null;
             Dictionary<string, string> scripts = HtmlScriptHelper.GetStartupScripts();
             if (scripts.Count >
                 && this.HttpContext.Response.ContentType == "text/html"
                 && this.HttpContext.Server.GetLastError() == null)
             {
                 var html = this.ReadOriginalHtml();
                 if (!string.IsNullOrEmpty(html))
                 {
                     string startupScripts = string.Empty;
                     foreach (string script in scripts.Values)
                     {
                         startupScripts += (script + Environment.NewLine);
                     }
                     if (!string.IsNullOrEmpty(startupScripts))
                     {
                         int endBodyIndex = html.LastIndexOf("</body>");
                         if (endBodyIndex != -)
                         {
                             html = html.Insert(endBodyIndex, startupScripts);
                         }
                     }
                 }

                 buffer = this.HttpContext.Response.ContentEncoding.GetBytes(html);

             }
             else
             {
                 this.Position = ;
                 buffer = this.GetBuffer();
             }

             this.OutputStream.Write(buffer, , buffer.Length);
             base.Close();
         }

         private string ReadOriginalHtml()
         {
             var html = string.Empty;
             Position = ;
             using (var reader = new StreamReader(this))
             {
                 html = reader.ReadToEnd();
             }

             return html;
         }
     }

     public class HtmlScriptHelper
     {
         private const string STARTUP_SCRIPTS = "STARTUP_SCRIPTS";
         public static bool IsStartupScriptRegistered(string key)
         {
             return GetStartupScripts().ContainsKey(key);
         }

         public static void RegisterStartupScript(string key, string script)
         {
             if (!IsStartupScriptRegistered(key))
             {
                 GetStartupScripts().Add(key, script);
             }
         }

         internal static Dictionary<string, string> GetStartupScripts()
         {
             Dictionary<string, string> scripts
                 = HttpContext.Current.Items[STARTUP_SCRIPTS] as Dictionary<string, string>;
             if (scripts == null)
             {
                 scripts = new Dictionary<string, string>();
                 HttpContext.Current.Items[STARTUP_SCRIPTS] = scripts;
             }

             return scripts;
         }
     }

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

 namespace ScriptHttpModule
 {
     public class MyFilter : IHttpModule
     {
         public void Dispose()
         {

         }

         public void Init(HttpApplication context)
         {
             context.BeginRequest += Context_BeginRequest;
             context.PreRequestHandlerExecute += Context_PreRequestHandlerExecute;
         }

         private void Context_BeginRequest(object sender, EventArgs e)
         {
             HttpContext httpContext = HttpContext.Current;
             string url = httpContext.Request.Url.AbsolutePath;
             if (!(url.EndsWith(".axd") || url.EndsWith(".ashx")
                 || url.EndsWith(".aspx") || url.EndsWith(".asmx")))
             {
                 httpContext.Response.Filter = new HtmlScriptStream(httpContext.Response.Filter, httpContext);
             }
         }

         private void Context_PreRequestHandlerExecute(object sender, EventArgs e)
         {
             HttpApplication application = (HttpApplication)sender;
             HttpContext context = application.Context;
             if (context != null)
             {
                 string sbScript1 = "<script type=\"text/javascript\">alert('a1');</script>";
                 string sbScript2 = "<script type=\"text/javascript\">alert('a2');</script>";
                 string sbScript3 = "<script type=\"text/javascript\">alert('a3');</script>";
                 Page thisPage = context.CurrentHandler as Page;

                 if (thisPage != null)
                 {
                     Type t = thisPage.GetType();

                     if (!thisPage.ClientScript.IsStartupScriptRegistered(t, "script-1"))
                     {
                         thisPage.ClientScript.RegisterStartupScript(t, "script-1", sbScript1);
                     }
                 }
                 else
                 {
                     HtmlScriptHelper.RegisterStartupScript("script-1", sbScript1);
                     HtmlScriptHelper.RegisterStartupScript("script-1", sbScript2);
                     HtmlScriptHelper.RegisterStartupScript("script-2", sbScript3);
                 }
             }
         }
     }
 }

下载附件：http://files.cnblogs.com/files/volnet/MvcHtmlScriptTest.rar