微软企业库5.0学习笔记（10）ASP.NET模块依赖注入_转载

时间：2011-03-17 来源：璞石攻玉

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。
      view plaincopy to clipboardprint?01.using System; 02.using System.Collections.Generic; 03.using System.Web; 04.using System.Web.UI; 05.using Microsoft.Practices.Unity; 06. 07.namespace Unity.Web 08.{ 09. public class UnityHttpModule : IHttpModule 10. { 11.    public void Init(HttpApplication context) 12.    { 13.      context.PreRequestHandlerExecute += OnPreRequestHandlerExecute; 14.    } 15. 16.    public void Dispose() { } 17. 18.    private void OnPreRequestHandlerExecute(object sender, EventArgs e) 19.    { 20.      IHttpHandler currentHandler = HttpContext.Current.Handler; 21.      HttpContext.Current.Application.GetContainer().BuildUp( 22.                          currentHandler.GetType(), currentHandler); 23. 24.      // User Controls are ready to be built up after page initialization is complete 25.      var currentPage = HttpContext.Current.Handler as Page; 26.      if (currentPage != null) 27.      { 28.        currentPage.InitComplete += OnPageInitComplete; 29.      } 30.    } 31. 32.    // Build up each control in the page's control tree 33.    private void OnPageInitComplete(object sender, EventArgs e) 34.    { 35.      var currentPage = (Page)sender; 36.      IUnityContainer container = HttpContext.Current.Application.GetContainer(); 37.      foreach (Control c in GetControlTree(currentPage)) 38.      { 39.        container.BuildUp(c.GetType(), c); 40.      } 41.      context.PreRequestHandlerExecute -= OnPreRequestHandlerExecute; 42.    } 43. 44.    // Get the controls in the page's control tree excluding the page itself 45.    private IEnumerable<Control> GetControlTree(Control root) 46.    { 47.      foreach (Control child in root.Controls) 48.      { 49.        yield return child; 50.        foreach (Control c in GetControlTree(child)) 51.        { 52.          yield return c; 53.        } 54.      } 55.    } 56. } 57.}        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。   view plaincopy to clipboardprint?01.using System.Web; 02.using Microsoft.Practices.Unity; 03. 04.namespace Unity.Web 05.{ 06. public static class HttpApplicationStateExtensions 07. { 08.    private const string GlobalContainerKey = "EntLibContainer"; 09. 10.    public static IUnityContainer GetContainer(this HttpApplicationState appState) 11.    { 12.      appState.Lock(); 13.      try 14.      { 15.        var myContainer = appState[GlobalContainerKey] as IUnityContainer; 16.        if (myContainer == null) 17.        { 18.          myContainer = new UnityContainer(); 19.          appState[GlobalContainerKey] = myContainer; 20.        } 21.        return myContainer; 22.      } 23.      finally 24.      { 25.          appState.UnLock(); 26.      } 27.    } 28. } 29.}

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