微软企业库5.0学习笔记（10）ASP.NET模块依赖注入

您可以使用HTTP模块，一个到ASP.NET HttpApplicationState类的扩展，在Global.asax编写代码强制ASP.NET在每一个页面请求时自动注入依赖的对象，就像在ASP.NET Web窗体应用程序中讨论的一样.
下列方法显示了一个合适的方法能够获取PreRequestHandlerExecute事件将它自己注入到ASP.NET的执行流水线，在每个页面请求中通过容器的BuildUp方法运行Http模块，并获取OnPageInitComplete事件。当OnPageInitComplete执行时模块代码按照所有的控件树运行，并通过容器的BuildUp方法处理每个控件。
BuildUp方法获取已经存在的对象实例，处理并填充类的依赖，返回实例。如果没有依赖则返回最初的实例。

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using Microsoft.Practices.Unity;

namespace Unity.Web
{
public class UnityHttpModule : IHttpModule
{
public void Init(HttpApplication context)
{
context.PreRequestHandlerExecute += OnPreRequestHandlerExecute;
}

public void Dispose() { }

private void OnPreRequestHandlerExecute(object sender, EventArgs e)
{
IHttpHandler currentHandler = HttpContext.Current.Handler;
HttpContext.Current.Application.GetContainer().BuildUp(
currentHandler.GetType(), currentHandler);

// User Controls are ready to be built up after page initialization is complete
var currentPage = HttpContext.Current.Handler as Page;
if (currentPage != null)
{
currentPage.InitComplete += OnPageInitComplete;
}
}

// Build up each control in the page's control tree
private void OnPageInitComplete(object sender, EventArgs e)
{
var currentPage = (Page)sender;
IUnityContainer container = HttpContext.Current.Application.GetContainer();
foreach (Control c in GetControlTree(currentPage))
{
container.BuildUp(c.GetType(), c);
}
context.PreRequestHandlerExecute -= OnPreRequestHandlerExecute;
}

// Get the controls in the page's control tree excluding the page itself
private IEnumerable<Control> GetControlTree(Control root)
{
foreach (Control child in root.Controls)
{
yield return child;
foreach (Control c in GetControlTree(child))
{
yield return c;
}
}
}
}
}
 

下面显示了一个应用程序状态的实现，并暴露一个静态的 GetContainer方法，这个方法能够在Application状态中创建一个新的统一容器，如果不存在的话，或者返回一个存在的实例的引用。   
using System.Web;
using Microsoft.Practices.Unity;

namespace Unity.Web
{
public static class HttpApplicationStateExtensions
{
private const string GlobalContainerKey = "EntLibContainer";

public static IUnityContainer GetContainer(this HttpApplicationState appState)
{
appState.Lock();
try
{
var myContainer = appState[GlobalContainerKey] as IUnityContainer;
if (myContainer == null)
{
myContainer = new UnityContainer();
appState[GlobalContainerKey] = myContainer;
}
return myContainer;
}
finally
{
appState.UnLock();
}
}
}
}
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