本文实例主要实现对已经生成了HTML的页面做一些输出到客户端之前的处理。
方法的实现原理是：把Response的输出重定向到自定义的容器内，也就是我们的StringBuilder对象里，在HTML所有的向页面输出都变成了向StringBuilder输出，然后我们对StringBuilder处理完成之后，再把Response的输出重定向到原来的页面上，然后再通过Response.Write方法把StringBuilder的内容输出到页面上。
这里之所以用反射，是因为Response对象的OutPut属性是只读的，通过反编译该类的程序集发现，OutPut实际上是内部私有成员 _writer来实现输出的。因此通过反射来改写该成员的值以实现输出流的重定向。
具体功能代码如下：
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using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.Text; using System.IO; using System.Reflection; public partial class _Default : System.Web.UI.Page { StringBuilder content = new StringBuilder(); TextWriter tw_old, tw_new; FieldInfo tw_field; protected void Page_Load(object sender, EventArgs e) { var context = HttpContext.Current; tw_old = context.Response.Output;//Response原来的OutPut tw_new = new StringWriter(content);//一个StringWriter,用来获取页面内容 var type_rp = context.Response.GetType(); //通过反射获取对象的私有字段 tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance); tw_field.SetValue(context.Response, tw_new); } protected override void Render(HtmlTextWriter writer) { base.Render(writer); //替换回Response的OutPut tw_field.SetValue(HttpContext.Current.Response, tw_old); //做自己的处理 content.AppendLine("<!--江湖小子-->"); HttpContext.Current.Response.Write(content.ToString()); } } |
方法二，用HttpModul来实现：
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using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.IO; using System.Text; using System.Reflection; /// <summary> ///HttpModule 的摘要说明 /// </summary> public class HttpModule : IHttpModule { private HttpApplication _contextApplication; private TextWriter tw_new, tw_old; private StringBuilder _content; private FieldInfo tw_field; public void Init(HttpApplication context) { _contextApplication = context; _contextApplication.PreRequestHandlerExecute += new EventHandler(_contextApplication_PreRequestHandlerExecute); } public void Dispose() { _contextApplication = null; _contextApplication.Dispose(); } public void _contextApplication_PreRequestHandlerExecute(object sender, EventArgs e) { HttpContext context = _contextApplication.Context; var _page = context.Handler as System.Web.UI.Page; _page.Unload += new EventHandler(_page_Unload); _content = new StringBuilder(); tw_old = context.Response.Output;//Response原来的OutPut tw_new = new StringWriter(_content);//一个StringWriter,用来获取页面内容 var type_rp = context.Response.GetType(); tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance); tw_field.SetValue(context.Response, tw_new); } void _page_Unload(object sender, EventArgs e) { //替换回Response的OutPut tw_field.SetValue(HttpContext.Current.Response, tw_old); //做自己的处理 _content.AppendLine("<!--江湖小子-->"); HttpContext.Current.Response.Write(_content.ToString()); } } |
方法三：
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public class HttpModule : IHttpModule { private HttpApplication _contextApplication; private TextWriter tw_new, tw_old; private StringBuilder _content; private FieldInfo tw_field; public void Init(HttpApplication application) { _contextApplication = application; _contextApplication.BeginRequest += new EventHandler(_contextApplication_BeginRequest); _contextApplication.EndRequest +=new EventHandler(_contextApplication_EndRequest); } void _contextApplication_BeginRequest(object sender, EventArgs e) { _content = new StringBuilder(); tw_old = _contextApplication.Response.Output; tw_new = new StringWriter(_content); var type_rp = _contextApplication.Response.GetType(); tw_field = type_rp.GetField("_writer", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance); tw_field.SetValue(_contextApplication.Response, tw_new); } void _contextApplication_EndRequest(object sender, EventArgs e) { tw_field.SetValue(_contextApplication.Response, tw_old); //做自己的处理 _content.AppendLine("<!--jhxz-->"); _contextApplication.Response.Write(_content.ToString()); } public void Dispose() { _contextApplication = null; _contextApplication.Dispose(); } } |
相信本文所述对大家的asp.net程序设计有一定的借鉴价值。
