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:
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:
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());
}
}