微软企业库5.0学习笔记（10）ASP.NET模块依赖注入

本文出自：http://blog.csdn.net/sfbirp/article/details/5621272

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();  
      }  
    }  
  }  
}