下面的两个示例演示如何使用 HttpApplication 类及其事件。第一个代码示例演示如何创建自定义 HTTP 模块以及如何将事件连接到该模块。第二代码示例演示如何修改 Web.config 文件。
下面的代码示例演示如何创建自定义 HTTP 模块并将 AcquireRequestState 事件连接到 HTTP 模块。HTTP 模块将截获对 Web 应用程序资源的所有请求，从而使您可以筛选客户端请求。预订 HttpApplication 事件的任何 HTTP 模块都必须实现 IHttpModule 接口。
Imports System
Imports System.Web
Namespace Samples.AspNet.VB
Public Class CustomHTTPModule
Implements IHttpModule
Public Sub New()
' Class constructor.
End Sub
' Classes that inherit IHttpModule
' must implement the Init and Dispose methods.
Public Sub Init(ByVal app As HttpApplication) Implements IHttpModule.Init
AddHandler app.AcquireRequestState, AddressOf app_AcquireRequestState
AddHandler app.PostAcquireRequestState, AddressOf app_PostAcquireRequestState
End Sub
Public Sub Dispose() Implements IHttpModule.Dispose
' Add code to clean up the
' instance variables of a module.
End Sub
' Define a custom AcquireRequestState event handler.
Public Sub app_AcquireRequestState(ByVal o As Object, ByVal ea As EventArgs)
Dim httpApp As HttpApplication = CType(o, HttpApplication)
Dim ctx As HttpContext = HttpContext.Current
ctx.Response.Write(" Executing AcquireRequestState ")
End Sub
' Define a custom PostAcquireRequestState event handler.
Public Sub app_PostAcquireRequestState(ByVal o As Object, ByVal ea As EventArgs)
Dim httpApp As HttpApplication = CType(o, HttpApplication)
Dim ctx As HttpContext = HttpContext.Current
ctx.Response.Write(" Executing PostAcquireRequestState ")
End Sub
End Class
End Namespace
using System;
using System.Web;
namespace Samples.AspNet.CS
{
public class CustomHTTPModule : IHttpModule
{
public CustomHTTPModule()
{
// Class constructor.
}
// Classes that inherit IHttpModule
// must implement the Init and Dispose methods.
public void Init(HttpApplication app)
{
app.AcquireRequestState += new EventHandler(app_AcquireRequestState);
app.PostAcquireRequestState += new EventHandler(app_PostAcquireRequestState);
}
public void Dispose()
{
// Add code to clean up the
// instance variables of a module.
}
// Define a custom AcquireRequestState event handler.
public void app_AcquireRequestState(object o, EventArgs ea)
{
HttpApplication httpApp = (HttpApplication)o;
HttpContext ctx = HttpContext.Current;
ctx.Response.Write(" Executing AcquireRequestState ");
}
// Define a custom PostAcquireRequestState event handler.
public void app_PostAcquireRequestState(object o, EventArgs ea)
{
HttpApplication httpApp = (HttpApplication)o;
HttpContext ctx = HttpContext.Current;
ctx.Response.Write(" Executing PostAcquireRequestState ");
}
}
}
在自定义 HTTP 模块中的事件可以发生之前，您必须先修改 Web.config 文件中的配置设置，通知 ASP.NET 有关该 HTTP 模块的信息。下面的代码示例演示 Web.config 文件的 httpModules 节中的相应配置设置。
<configuration>
<system.web>
<httpModules>
<add type="Samples.AspNet.CS.CustomHTTPModule"
name="CustomHttpModule" />
</httpModules>
</system.web>
</configuration>
<configuration>
<system.web>
<httpModules>
<add type="Samples.AspNet.VB.CustomHTTPModule"
name="CustomHttpModule" />
</httpModules>
</system.web>
</configuration>