本文實例主要實現對已經生成了HTML的頁面做一些輸出到客戶端之前的處理。
方法的實現原理是：把Response的輸出重定向到自定義的容器內，也就是我們的StringBuilder對象里，在HTML所有的向頁面輸出都變成了向StringBuilder輸出，然后我們對StringBuilder處理完成之后，再把Response的輸出重定向到原來的頁面上，然后再通過Response.Write方法把StringBuilder的內容輸出到頁面上。
這里之所以用反射，是因為Response對象的OutPut屬性是只讀的，通過反編譯該類的程序集發現，OutPut實際上是內部私有成員 _writer來實現輸出的。因此通過反射來改寫該成員的值以實現輸出流的重定向。
具體功能代碼如下：
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原來的OutPut
tw_new = new StringWriter(content);//一個StringWriter,用來獲取頁面內容
var type_rp = context.Response.GetType();
//通過反射獲取對象的私有字段
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);
//替換回Response的OutPut
tw_field.SetValue(HttpContext.Current.Response, tw_old);
//做自己的處理
content.AppendLine("!--江湖小子-->");
HttpContext.Current.Response.Write(content.ToString());
}
}
方法二，用HttpModul來實現：
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 的摘要說明
/// /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原來的OutPut
tw_new = new StringWriter(_content);//一個StringWriter,用來獲取頁面內容
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)
{
//替換回Response的OutPut
tw_field.SetValue(HttpContext.Current.Response, tw_old);
//做自己的處理
_content.AppendLine("!--江湖小子-->");
HttpContext.Current.Response.Write(_content.ToString());
}
}
方法三：
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);
//做自己的處理
_content.AppendLine("!--jhxz-->");
_contextApplication.Response.Write(_content.ToString());
}
public void Dispose()
{
_contextApplication = null;
_contextApplication.Dispose();
}
}
相信本文所述對大家的asp.net程序設計有一定的借鑒價值。
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