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 > 0 
                && 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 != -1)
                        {
                            html = html.Insert(endBodyIndex, startupScripts);
                        }
                    }
                }

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

            }
            else
            {
                this.Position = 0;
                buffer = this.GetBuffer();
            }

            this.OutputStream.Write(buffer, 0, buffer.Length);
            base.Close();
        }

        private string ReadOriginalHtml()
        {
            var html = string.Empty;
            Position = 0;
            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：https://files.cnblogs.com/files/volnet/MvcHtmlScriptTest.rar