ASP.NET MVC Preview生命周期分析
做ASP.NET WebForm开发都知道，ASP.NET有复杂的生命周期，学习ASP.NET MVC就要深入理解它的生命周期。今天从CodePlex上下载了ASP.NET Preview 2 的源代码，还有两个程序集Routing与Abstractions并未发布，不过这两个程序集的类并不多，可以用NET反编译工具 Reflector解开来看看，可惜这两个程序集用的是VS2008使用.net 3.5开发的，用了c# 3.0的很多特性，Reflector反编译不完全。
ASP.NET MVC通过HttpModule（UrlRoutingModule）开始他的执行流程
<httpModules> <add name="UrlRoutingModule" type="System.Web.Routing.UrlRoutingModule, System.Web.Routing" /></httpModules> 代码如下：
namespace System.Web.Routing
{
using System; using System.Globalization; using System.Runtime.CompilerServices; using System.Security.Permissions; using System.Web; using System.Web.Resources; [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal), AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)] public class UrlRoutingModule : IHttpModule
{ private static readonly object _requestDataKey = new object(); private System.Web.Routing.RouteCollection _routeCollection; protected virtual void Dispose() {
} protected virtual void Init(HttpApplication application) { application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache); application.PostMapRequestHandler += new EventHandler(this.OnApplicationPostMapRequestHandler); } private void OnApplicationPostMapRequestHandler(object sender, EventArgs e) { HttpContextBase context = new HttpContextWrapper2(((HttpApplication) sender).Context); this.PostMapRequestHandler(context); } private void OnApplicationPostResolveRequestCache(object sender, EventArgs e) { HttpContextBase context = new HttpContextWrapper2(((HttpApplication) sender).Context); this.PostResolveRequestCache(context); } public virtual void PostMapRequestHandler(HttpContextBase context) { RequestData data = (RequestData) context.Items[_requestDataKey]; if (data != null) { context.RewritePath(data.OriginalPath); context.Handler = data.HttpHandler; } } public virtual void PostResolveRequestCache(HttpContextBase context) { RouteData routeData = this.RouteCollection.GetRouteData(context); if (routeData != null) { IRouteHandler routeHandler = routeData.RouteHandler; if (routeHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, RoutingResources.UrlRoutingModule_NoRouteHandler, new object[0])); } RequestContext requestContext = new RequestContext(context, routeData); IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext); if (httpHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, RoutingResources.UrlRoutingModule_NoHttpHandler, new object[] { routeHandler.GetType() })); } RequestData data2 = new RequestData(); data2.OriginalPath = context.Request.Path; data2.HttpHandler = httpHandler; context.Items[_requestDataKey] = data2; context.RewritePath("~/UrlRouting.axd"); } } void IHttpModule.Dispose() { this.Dispose(); } void IHttpModule.Init(HttpApplication application) { this.Init(application); } public System.Web.Routing.RouteCollection RouteCollection { get { if (this._routeCollection == null) { this._routeCollection = RouteTable.Routes; } return this._routeCollection; } set { this._routeCollection = value; } } }
里面还定义了一个RequestData，主要就是当前处理的HttpHandler和URL原始路径。来看看ASP.NET 的HttpApplication 管线会依次处理下面的请求:
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对请求进行验证，将检查浏览器发送的信息，并确定其是否包含潜在恶意标记。
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如果已在 Web.config 文件的 UrlMappingsSection 节中配置了任何 URL，则执行 URL 映射。
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引发 BeginRequest 事件。
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引发 AuthenticateRequest 事件。
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引发 PostAuthenticateRequest 事件。
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引发 AuthorizeRequest 事件。
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引发 PostAuthorizeRequest 事件。
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引发 ResolveRequestCache 事件。
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引发 PostResolveRequestCache 事件。
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根据所请求资源的文件扩展名（在应用程序的配置文件中映射），选择实现 IHttpHandler 的类，对请求进行处理。如果该请求针对从 Page 类派生的对象（页），并且需要对该页进行编译，则 ASP.NET 会在创建该页的实例之前对其进行编译。
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引发 PostMapRequestHandler 事件。
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引发 AcquireRequestState 事件。
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引发 PostAcquireRequestState 事件。
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引发 PreRequestHandlerExecute 事件。
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为该请求调用合适的 IHttpHandler 类的 ProcessRequest 方法（或异步版 BeginProcessRequest）。例如，如果该请求针对某页，则当前的页实例将处理该请求。
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引发 PostRequestHandlerExecute 事件。
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引发 ReleaseRequestState 事件。
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引发 PostReleaseRequestState 事件。
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如果定义了 Filter 属性，则执行响应筛选。
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引发 UpdateRequestCache 事件。
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引发 PostUpdateRequestCache 事件。
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引发 EndRequest 事件。
上述UrlRoutingModule订阅了两个 HttpApplication 事件，PostResolveRequestCache 要比 PostMapRequestHandler 更早执行，先看PostResolveRequestCache 事件，他首先从首先从 RouteCollection 中获取一个 RouteData 对象。看看RouteCollection 属性：
public System.Web.Routing.RouteCollection RouteCollection { get { if (this._routeCollection == null) { this._routeCollection = RouteTable.Routes; } return this._routeCollection; } set { this._routeCollection = value; } } 看到了来自RouteTable，这不正是在Global.asax.cs 中添加的 Route 集合:
protected void Application_Start(object sender, EventArgs e) { RegisterRoutes(RouteTable.Routes); CreateDefaultUserIfNotExists(); } public static void RegisterRoutes(RouteCollection routes) { int iisVersion = Convert.ToInt32(ConfigurationManager.AppSettings["IISVersion"], System.Globalization.CultureInfo.InvariantCulture); if (iisVersion >= 7) { RegisterRoutesForNewIIS(routes); } else { RegisterRoutesForOldIIS(routes); } } private static void RegisterRoutesForNewIIS(ICollection<RouteBase> routes) { routes.Add(new Route("User/Login", new RouteValueDictionary(new { controller = "User", action = "Login" }), new MvcRouteHandler())); routes.Add(new Route("User/Logout", new RouteValueDictionary(new { controller = "User", action = "Logout" }), new MvcRouteHandler())); routes.Add(new Route("User/Signup", new RouteValueDictionary(new { controller = "User", action = "Signup" }), new MvcRouteHandler())); routes.Add(new Route("User/SendPassword", new RouteValueDictionary(new { controller = "User", action = "SendPassword" }), new MvcRouteHandler())); routes.Add(new Route("Story/Detail/{id}", new RouteValueDictionary(new { controller = "Story", action = "Detail" }), new MvcRouteHandler())); routes.Add(new Route("Story/Upcoming/{page}", new RouteValueDictionary(new { controller = "Story", action = "Upcoming" }), new MvcRouteHandler())); routes.Add(new Route("Story/Search/{q}/{page}", new RouteValueDictionary(new { controller = "Story", action = "Search" }), new MvcRouteHandler())); var defaults = new RouteValueDictionary ( new { controller = "Story", action = "Category", name = (string)null, page = (int?)null } ); routes.Add(new Route("Story/Category/{page}", defaults, new MvcRouteHandler())); routes.Add(new Route("Story/{action}/{name}/{page}", defaults, new MvcRouteHandler())); routes.Add(new Route("{controller}/{action}/{id}", defaults, new MvcRouteHandler())); routes.Add(new Route("Default.aspx", defaults, new MvcRouteHandler())); } private static void RegisterRoutesForOldIIS(ICollection<RouteBase> routes) { routes.Add(new Route("User.mvc/Login", new RouteValueDictionary(new { controller = "User", action = "Login" }), new MvcRouteHandler())); routes.Add(new Route("User.mvc/Logout", new RouteValueDictionary(new { controller = "User", action = "Logout" }), new MvcRouteHandler())); routes.Add(new Route("User.mvc/Signup", new RouteValueDictionary(new { controller = "User", action = "Signup" }), new MvcRouteHandler())); routes.Add(new Route("User.mvc/SendPassword", new RouteValueDictionary(new { controller = "User", action = "SendPassword" }), new MvcRouteHandler())); routes.Add(new Route("Story.mvc/Detail/{id}", new RouteValueDictionary(new { controller = "Story", action = "Detail" }), new MvcRouteHandler())); routes.Add(new Route("Story.mvc/Upcoming/{page}", new RouteValueDictionary(new { controller = "Story", action = "Upcoming" }), new MvcRouteHandler())); routes.Add(new Route("Story.mvc/Search/{q}/{page}", new RouteValueDictionary(new { controller = "Story", action = "Search" }), new MvcRouteHandler())); var defaults = new RouteValueDictionary( new { controller = "Story", action = "Category", name = (string)null, page = (int?)null } ); routes.Add(new Route("Story.mvc/Category/{page}", defaults, new MvcRouteHandler())); routes.Add(new Route("Story.mvc/{action}/{name}/{page}", defaults, new MvcRouteHandler())); routes.Add(new Route("{controller}.mvc/{action}/{id}", defaults, new MvcRouteHandler())); routes.Add(new Route("Default.aspx", defaults, new MvcRouteHandler())); } 上述代码来自[翻译]使用asp.net mvc再造一个digg 第一部分的kigg。回到上文，在获取 RoteCollection 之后，通过调用 GetRouteData(context) 返回一个 RouteData 对象，该对象内部包含了我们注册 Route 时的相关设置，包括下面所需要的 MvcRouteHandler。接下来，该方法将 routeData 和上下文一起打包成 RequestContext，这就是为相关处理准备的上下文环境。通过调用 IRouteHandler.GetHttpHandler() 方法，终于到达流程的关键IHttpHandler（MvcHandler）。在WebForm中我们知道每一个页面都是一个HttpHandler，Asp.net mvc也不例外。
先来看看MvcRouteHandler：
namespace System.Web.Mvc { using System.Web.Routing; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class MvcRouteHandler : IRouteHandler { protected virtual IHttpHandler GetHttpHandler(RequestContext requestContext) { return new MvcHandler(requestContext); } 
IRouteHandler Members }} 这里得到了MvcHandler:
namespace System.Web.Mvc { using System.Globalization; using System.Web.Mvc.Resources; using System.Web.Routing; using System.Web.SessionState; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class MvcHandler : IHttpHandler, IRequiresSessionState { private ControllerBuilder _controllerBuilder; public MvcHandler(RequestContext requestContext) { if (requestContext == null) { throw new ArgumentNullException("requestContext"); } RequestContext = requestContext; } protected virtual bool IsReusable { get { // REVIEW: What's this? return false; } } internal ControllerBuilder ControllerBuilder { get { if (_controllerBuilder == null) { _controllerBuilder = ControllerBuilder.Current; } return _controllerBuilder; } set { _controllerBuilder = value; } } public RequestContext RequestContext { get; private set; } protected virtual void ProcessRequest(HttpContext httpContext) { HttpContextBase iHttpContext = new HttpContextWrapper2(httpContext); ProcessRequest(iHttpContext); } protected internal virtual void ProcessRequest(HttpContextBase httpContext) { // Get the controller type string controllerName = RequestContext.RouteData.GetRequiredString("controller"); // Instantiate the controller and call Execute IControllerFactory factory = ControllerBuilder.GetControllerFactory(); IController controller = factory.CreateController(RequestContext, controllerName); if (controller == null) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.ControllerBuilder_FactoryReturnedNull, factory.GetType(), controllerName)); } try { ControllerContext controllerContext = new ControllerContext(RequestContext, controller); controller.Execute(controllerContext); } finally { factory.DisposeController(controller); } } IHttpHandler Members }} RequestData data2 = new RequestData(); data2.OriginalPath = context.Request.Path; data2.HttpHandler = httpHandler; context.Items[_requestDataKey] = data2; context.RewritePath("~/UrlRouting.axd"); OnApplicationPostMapRequestHandler 被执行。在 PostMapRequestHandler 中，它提取了前面预先准备好的上下文，并修改了 HttpContext.Handler，使得 MvcHandler 接管默认的WebForm的HttpHandler，才是执行ASP.NET MVC的流程。现在来继续看MvcHandler。
首先从 RouteData 中提取 Controller 的名字(这个名字是我们在 Global.asax.cs RegisterRoutes 中注册 Route 时提供的)，然后获取 ControllerFactory，只不过这里面专门提供了一个 ControllerBuilder。
internal ControllerBuilder ControllerBuilder { get { if (_controllerBuilder == null) { _controllerBuilder = ControllerBuilder.Current; } return _controllerBuilder; } set { _controllerBuilder = value; } } 如果我们自定义MvcHandler，则需要好好的看看ControllerBuilder.Current：
namespace System.Web.Mvc { using System; using System.Diagnostics.CodeAnalysis; using System.Globalization; using System.Web; using System.Web.Mvc.Resources; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class ControllerBuilder { private static ControllerBuilder _instance = new ControllerBuilder(); private Func<IControllerFactory> _factoryThunk; public ControllerBuilder() { SetControllerFactory(new DefaultControllerFactory()); } public static ControllerBuilder Current { get { return _instance; } } [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate", Justification = "Calling method multiple times might return different objects.")] public IControllerFactory GetControllerFactory() { IControllerFactory controllerFactoryInstance = _factoryThunk(); return controllerFactoryInstance; } public void SetControllerFactory(IControllerFactory controllerFactory) { if (controllerFactory == null) { throw new ArgumentNullException("controllerFactory"); } _factoryThunk = () => controllerFactory; } public void SetControllerFactory(Type controllerFactoryType) { if (controllerFactoryType == null) { throw new ArgumentNullException("controllerFactoryType"); } if (!typeof(IControllerFactory).IsAssignableFrom(controllerFactoryType)) { throw new ArgumentException( String.Format( CultureInfo.CurrentUICulture, MvcResources.ControllerBuilder_MissingIControllerFactory, controllerFactoryType), "controllerFactoryType"); } _factoryThunk = delegate() { try { return (IControllerFactory) Activator.CreateInstance(controllerFactoryType); } catch (Exception ex) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.ControllerBuilder_ErrorCreatingControllerFactory, controllerFactoryType), ex); } }; } }} (1) 通常情况下，返回一个默认的 DefaultControllerFactory 实例。
(2) 我们可以在 Application_Start 中通过 ControllerBuilder.Current.SetControllerFactory 方法来注册一个我们自定义的工厂。
(3) 核心代码: factory = (IControllerFactory)Activator.CreateInstance(controllerFactoryType)，通过反射创建IControllerFactory;
回到MvcHandler的 ProcessRequest ，DefaultControllerFactory.CreateController(RequestContext, requiredString) 来返回 IController 实例。下面看看DefaultControllerFactory的代码：
通过反射来创建 Controller 实例，GetControllerType 里面做了些缓存处理，以此来避免频繁使用反射造成的性能问题。继续MvcHandler.ProcessRequest()，在得到控制器实例后，MvcHandler 开始了调用 Controller.Execute() 来进一步后续操作，同时对其上下文进一步封装，除了前面创建的 RequestContext，还加上了当前这个 Controller 对象的引用，类名叫ControllerContext。
namespace System.Web.Mvc { using System.Web.Routing; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class ControllerContext : RequestContext { public ControllerContext(HttpContextBase httpContext, RouteData routeData, IController controller) : base(httpContext, routeData) { if (controller == null) { throw new ArgumentNullException("controller"); } Controller = controller; } public ControllerContext(RequestContext requestContext, IController controller) : this(GetRequestContext(requestContext).HttpContext, GetRequestContext(requestContext).RouteData, controller) { } public IController Controller { get; private set; } internal static RequestContext GetRequestContext(RequestContext requestContext) { if (requestContext == null) { throw new ArgumentNullException("requestContext"); } return requestContext; } }} 继续看IController的默认实现类Controller：
namespace System.Web.Mvc { using System; using System.Collections.Generic; using System.ComponentModel; using System.Diagnostics.CodeAnalysis; using System.Globalization; using System.Reflection; using System.Security.Principal; using System.Web; using System.Web.Mvc.Resources; using System.Web.Routing; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class Controller : IController { private RouteCollection _routeCollection; private IDictionary<string, object> _viewData; private IViewEngine _viewEngine; public ControllerContext ControllerContext { get; set; } public HttpContextBase HttpContext { get { return ControllerContext == null ? null : ControllerContext.HttpContext; } } public HttpRequestBase Request { get { return HttpContext == null ? null : HttpContext.Request; } } public HttpResponseBase Response { get { return HttpContext == null ? null : HttpContext.Response; } } internal RouteCollection RouteCollection { get { if (_routeCollection == null) { _routeCollection = RouteTable.Routes; } return _routeCollection; } set { _routeCollection = value; } } public RouteData RouteData { get { return ControllerContext == null ? null : ControllerContext.RouteData; } } public HttpServerUtilityBase Server { get { return HttpContext == null ? null : HttpContext.Server; } } [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly", Justification = "This property is settable so that unit tests can provide mock implementations.")] public TempDataDictionary TempData { get; set; } public IPrincipal User { get { return HttpContext == null ? null : HttpContext.User; } } public IDictionary<string, object> ViewData { get { if (_viewData == null) { _viewData = new Dictionary<string, object>(); } return _viewData; } } public IViewEngine ViewEngine { get { return _viewEngine ?? new WebFormViewEngine(); } set { if (value == null) { throw new ArgumentNullException("value"); } _viewEngine = value; } } private static object ConvertParameterType(object value, Type destinationType, string parameterName, string actionName) { if (value == null || value.GetType() == destinationType) { return value; } TypeConverter converter = TypeDescriptor.GetConverter(destinationType); bool canConvertFrom = converter.CanConvertFrom(value.GetType()); if (!canConvertFrom) { converter = TypeDescriptor.GetConverter(value.GetType()); } if (!(canConvertFrom || converter.CanConvertTo(destinationType))) { throw new InvalidOperationException(String.Format( CultureInfo.CurrentUICulture, MvcResources.Controller_CannotConvertParameter, parameterName, actionName, value, destinationType)); } try { return canConvertFrom ? converter.ConvertFrom(value) : converter.ConvertTo(value, destinationType); } catch (Exception ex) { throw new InvalidOperationException(String.Format( CultureInfo.CurrentUICulture, MvcResources.Controller_CannotConvertParameter, parameterName, actionName, value, destinationType), ex); } } protected internal virtual void Execute(ControllerContext controllerContext) { if (controllerContext == null) { throw new ArgumentNullException("controllerContext"); } ControllerContext = controllerContext; TempData = new TempDataDictionary(controllerContext.HttpContext); string actionName = RouteData.GetRequiredString("action"); if (!InvokeAction(actionName)) { HandleUnknownAction(actionName); } } protected internal virtual void HandleUnknownAction(string actionName) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_UnknownAction, actionName)); } protected internal bool InvokeAction(string actionName) { return InvokeAction(actionName, new RouteValueDictionary()); } protected internal virtual bool InvokeAction(string actionName, RouteValueDictionary values) { if (String.IsNullOrEmpty(actionName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName"); } // We have to loop through all the methods to make sure there isn't // a conflict. If we stop the loop the first time we find a match // we might miss some error cases. MemberInfo[] membInfos = GetType().GetMember(actionName, MemberTypes.Method, BindingFlags.IgnoreCase | BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public); MethodInfo foundMatch = null; foreach (MemberInfo memberInfo in membInfos) { MethodInfo mi = (MethodInfo)memberInfo; // 1) Action methods must not have the non-action attribute in their inheritance chain, and // 2) special methods like constructors, property accessors, and event accessors cannot be action methods, and // 3) methods originally defined on Object (like ToString) or Controller cannot be action methods. if (!mi.IsDefined(typeof(NonActionAttribute), true) && !mi.IsSpecialName && mi.DeclaringType.IsSubclassOf(typeof(Controller))) { if (foundMatch != null) { throw new InvalidOperationException( String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MoreThanOneAction, actionName, GetType())); } foundMatch = mi; } } if (foundMatch != null) { InvokeActionMethod(foundMatch, values); return true; } return false; } [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "We use MethodInfo since it represents only methods and not constructors." + "This method only makes sense for use with methods.")] protected internal virtual void InvokeActionMethod(MethodInfo methodInfo, RouteValueDictionary values) { if (methodInfo == null) { throw new ArgumentNullException("methodInfo"); } if (values == null) { values = new RouteValueDictionary(); } if (methodInfo.ContainsGenericParameters) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_ActionCannotBeGeneric, methodInfo.Name)); } ParameterInfo[] methodParameters = methodInfo.GetParameters(); object[] parameterValues = null; if (methodParameters.Length > 0) { parameterValues = new object[methodParameters.Length]; for (int i = 0; i < methodParameters.Length; i++) { ParameterInfo pi = methodParameters[i]; if (pi.IsOut || pi.ParameterType.IsByRef) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_ReferenceParametersNotSupported, pi.Name, methodInfo.Name)); } bool valueRequired = true; if (pi.ParameterType.IsClass) { // Classes (ref types) don't require values since we can pass in null valueRequired = false; } else { if ((pi.ParameterType.IsGenericType && !pi.ParameterType.IsGenericTypeDefinition) && (pi.ParameterType.GetGenericTypeDefinition() == typeof(Nullable<>))) { // Nullable types don't require values since we can pass in null valueRequired = false; } } // Try to get a value for the parameter. We use this order of precedence: // 1. Explicitly-provided extra parameters in the call to InvokeAction() // 2. Values from the RouteData (could be from the typed-in URL or from the route's default values) // 3. Request values (query string, form post data, cookie) object parameterValue = null; if (!values.TryGetValue(methodParameters[i].Name, out parameterValue)) { if (RouteData == null || !RouteData.Values.TryGetValue(methodParameters[i].Name, out parameterValue)) { if (Request != null) { parameterValue = Request[methodParameters[i].Name]; } } } if (parameterValue == null && valueRequired) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MissingParameter, pi.Name, methodInfo.Name)); } try { parameterValues[i] = ConvertParameterType(parameterValue, methodParameters[i].ParameterType, methodParameters[i].Name, methodInfo.Name); } catch (Exception ex) { // Parameter value conversion errors are acceptable unless the value is required if (valueRequired) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MissingParameter, pi.Name, methodInfo.Name), ex); } } } } InvokeActionMethodFilters(methodInfo, () => methodInfo.Invoke(this, parameterValues)); } private void InvokeActionMethodFilters(MethodInfo methodInfo, Action continuation) { // filters should execute in this order: // controller virtual overrides -> controller base attributes -> controller type attributes -> // base action method attributes -> action method attributes List<ActionFilterAttribute> filters = new List<ActionFilterAttribute>() { new ControllerActionFilter(this) }; Stack<MemberInfo> memberChain = new Stack<MemberInfo>(); Type curType = GetType(); while (curType != null) { memberChain.Push(curType); curType = curType.BaseType; } List<ActionFilterAttribute> sortedClassFilters = SortActionFilters(memberChain); filters.AddRange(sortedClassFilters); List<ActionFilterAttribute> sortedMethodFilters = PrepareMethodActionFilters(methodInfo); filters.AddRange(sortedMethodFilters); FilterContext context = new FilterContext(ControllerContext, methodInfo); ActionFilterExecutor executor = new ActionFilterExecutor(filters, context, continuation); executor.Execute(); } protected virtual void OnActionExecuted(FilterExecutedContext filterContext) { } protected virtual void OnActionExecuting(FilterExecutingContext filterContext) { } internal static List<ActionFilterAttribute> PrepareMethodActionFilters(MethodInfo methodInfo) { Stack<MemberInfo> memberChain = new Stack<MemberInfo>(); memberChain.Push(methodInfo); MethodInfo baseMethod = methodInfo.GetBaseDefinition(); Type curType = methodInfo.DeclaringType.BaseType; while (true) { MemberInfo[] membInfos = curType.GetMember(methodInfo.Name, MemberTypes.Method, BindingFlags.IgnoreCase | BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public); MethodInfo foundMatch = null; foreach (MemberInfo memberInfo in membInfos) { MethodInfo mi = (MethodInfo)memberInfo; if (mi.GetBaseDefinition() == baseMethod && mi.DeclaringType == curType) { foundMatch = mi; break; } } if (foundMatch == null) { break; } memberChain.Push(foundMatch); curType = curType.BaseType; } return SortActionFilters(memberChain); } protected virtual void RedirectToAction(RouteValueDictionary values) { VirtualPathData vpd = RouteCollection.GetVirtualPath(ControllerContext, values); string target = null; if (vpd != null) { target = vpd.VirtualPath; } HttpContext.Response.Redirect(target); } protected void RedirectToAction(string actionName) { if (String.IsNullOrEmpty(actionName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName"); } RouteValueDictionary valuesDictionary = new RouteValueDictionary(); valuesDictionary.Add("action", actionName); RedirectToAction(valuesDictionary); } protected void RedirectToAction(string actionName, string controllerName) { if (String.IsNullOrEmpty(actionName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName"); } if (String.IsNullOrEmpty(controllerName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName"); } RouteValueDictionary valuesDictionary = new RouteValueDictionary(); valuesDictionary.Add("action", actionName); valuesDictionary.Add("controller", controllerName); RedirectToAction(valuesDictionary); } protected void RenderView(string viewName) { RenderView(viewName, String.Empty, ViewData); } protected void RenderView(string viewName, string masterName) { RenderView(viewName, masterName, ViewData); } protected void RenderView(string viewName, object viewData) { RenderView(viewName, String.Empty, viewData); } protected virtual void RenderView(string viewName, string masterName, object viewData) { ViewContext viewContext = new ViewContext(ControllerContext, viewName, masterName, viewData, TempData); ViewEngine.RenderView(viewContext); } private static List<ActionFilterAttribute> SortActionFilters(Stack<MemberInfo> memberChain) { List<ActionFilterAttribute> filters = new List<ActionFilterAttribute>(); foreach (MemberInfo member in memberChain) { ActionFilterAttribute[] attrs = (ActionFilterAttribute[])member.GetCustomAttributes(typeof(ActionFilterAttribute), false /* inherit */); SortedList<int, ActionFilterAttribute> orderedFilters = new SortedList<int, ActionFilterAttribute>(); foreach (ActionFilterAttribute filter in attrs) { // filters are allowed to have the same order only if the order is -1. in that case, // they are processed before explicitly ordered filters but in no particular order in // relation to one another. if (filter.Order >= 0) { if (orderedFilters.ContainsKey(filter.Order)) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.ActionFilter_DuplicateOrder, member, filter.Order)); } orderedFilters.Add(filter.Order, filter); } else { filters.Add(filter); } } filters.AddRange(orderedFilters.Values); } return filters; } IController Members private sealed class ControllerActionFilter : ActionFilterAttribute { private Controller _controller; public ControllerActionFilter(Controller controller) { _controller = controller; } public override void OnActionExecuted(FilterExecutedContext filterContext) { _controller.OnActionExecuted(filterContext); } public override void OnActionExecuting(FilterExecutingContext filterContext) { _controller.OnActionExecuting(filterContext); } } }} 获取 Action 的名字，然后开始执行 InvokeAction，如果找不到Action，则调用HandleUnknownAction，这是一个虚拟方法，可以在子类中重写，默认是抛出一个异常InvalidOperationException。
protected internal virtual void Execute(ControllerContext controllerContext) { if (controllerContext == null) { throw new ArgumentNullException("controllerContext"); } ControllerContext = controllerContext; TempData = new TempDataDictionary(controllerContext.HttpContext); string actionName = RouteData.GetRequiredString("action"); if (!InvokeAction(actionName)) { HandleUnknownAction(actionName); } } 详细看看InvokeAction方式的执行：
protected internal bool InvokeAction(string actionName) { return InvokeAction(actionName, new RouteValueDictionary()); } protected internal virtual bool InvokeAction(string actionName, RouteValueDictionary values) { if (String.IsNullOrEmpty(actionName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName"); } // We have to loop through all the methods to make sure there isn't // a conflict. If we stop the loop the first time we find a match // we might miss some error cases. MemberInfo[] membInfos = GetType().GetMember(actionName, MemberTypes.Method, BindingFlags.IgnoreCase | BindingFlags.InvokeMethod | BindingFlags.Instance | BindingFlags.Public); MethodInfo foundMatch = null; foreach (MemberInfo memberInfo in membInfos) { MethodInfo mi = (MethodInfo)memberInfo; // 1) Action methods must not have the non-action attribute in their inheritance chain, and // 2) special methods like constructors, property accessors, and event accessors cannot be action methods, and // 3) methods originally defined on Object (like ToString) or Controller cannot be action methods. if (!mi.IsDefined(typeof(NonActionAttribute), true) && !mi.IsSpecialName && mi.DeclaringType.IsSubclassOf(typeof(Controller))) { if (foundMatch != null) { throw new InvalidOperationException( String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MoreThanOneAction, actionName, GetType())); } foundMatch = mi; } } if (foundMatch != null) { InvokeActionMethod(foundMatch, values); return true; } return false; } 它通过反射获取所有同名 Action 方法信息；其次，它过滤掉所有有 NonActionAttribute 和 IsSpecialName 标记的方法；第三，当同名有效 Action 被重载时它会抛出异常（提示Controller_MoreThanOneAction），继续调用InvokeActionMethod：
[SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "We use MethodInfo since it represents only methods and not constructors." + "This method only makes sense for use with methods.")]protected internal virtual void InvokeActionMethod(MethodInfo methodInfo, RouteValueDictionary values) { if (methodInfo == null) { throw new ArgumentNullException("methodInfo"); } if (values == null) { values = new RouteValueDictionary(); } if (methodInfo.ContainsGenericParameters) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_ActionCannotBeGeneric, methodInfo.Name)); } ParameterInfo[] methodParameters = methodInfo.GetParameters(); object[] parameterValues = null; if (methodParameters.Length > 0) { parameterValues = new object[methodParameters.Length]; for (int i = 0; i < methodParameters.Length; i++) { ParameterInfo pi = methodParameters[i]; if (pi.IsOut || pi.ParameterType.IsByRef) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_ReferenceParametersNotSupported, pi.Name, methodInfo.Name)); } bool valueRequired = true; if (pi.ParameterType.IsClass) { // Classes (ref types) don't require values since we can pass in null valueRequired = false; } else { if ((pi.ParameterType.IsGenericType && !pi.ParameterType.IsGenericTypeDefinition) && (pi.ParameterType.GetGenericTypeDefinition() == typeof(Nullable<>))) { // Nullable types don't require values since we can pass in null valueRequired = false; } } // Try to get a value for the parameter. We use this order of precedence: // 1. Explicitly-provided extra parameters in the call to InvokeAction() // 2. Values from the RouteData (could be from the typed-in URL or from the route's default values) // 3. Request values (query string, form post data, cookie) object parameterValue = null; if (!values.TryGetValue(methodParameters[i].Name, out parameterValue)) { if (RouteData == null || !RouteData.Values.TryGetValue(methodParameters[i].Name, out parameterValue)) { if (Request != null) { parameterValue = Request[methodParameters[i].Name]; } } } if (parameterValue == null && valueRequired) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MissingParameter, pi.Name, methodInfo.Name)); } try { parameterValues[i] = ConvertParameterType(parameterValue, methodParameters[i].ParameterType, methodParameters[i].Name, methodInfo.Name); } catch (Exception ex) { // Parameter value conversion errors are acceptable unless the value is required if (valueRequired) { throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.Controller_MissingParameter, pi.Name, methodInfo.Name), ex); } } } } InvokeActionMethodFilters(methodInfo, () => methodInfo.Invoke(this, parameterValues));}InvokeActionMethodFilters(methodInfo, () => methodInfo.Invoke(this, parameterValues));
这行代码将 Action 的调用作为一个委托，连同反射信息传递给 InvokeActionMethodFilters。
private void InvokeActionMethodFilters(MethodInfo methodInfo, Action continuation) { // filters should execute in this order: // controller virtual overrides -> controller base attributes -> controller type attributes -> // base action method attributes -> action method attributes List<ActionFilterAttribute> filters = new List<ActionFilterAttribute>() { new ControllerActionFilter(this) }; Stack<MemberInfo> memberChain = new Stack<MemberInfo>(); Type curType = GetType(); while (curType != null) { memberChain.Push(curType); curType = curType.BaseType; } List<ActionFilterAttribute> sortedClassFilters = SortActionFilters(memberChain); filters.AddRange(sortedClassFilters); List<ActionFilterAttribute> sortedMethodFilters = PrepareMethodActionFilters(methodInfo); filters.AddRange(sortedMethodFilters); FilterContext context = new FilterContext(ControllerContext, methodInfo); ActionFilterExecutor executor = new ActionFilterExecutor(filters, context, continuation); executor.Execute(); } 这个方法首先将默认的过滤器 ControllerActionFilter 加到列表，然后提取所有继承层次上基类的过滤器特性。最后将这些过滤器集合、过滤上下文，连同前一个方法传递进来的 Action 执行委托(continuation) 再次转交给了一个 ActionFilterExecutor 对象实例，并调用其 Execute 方法。
ExecuteRecursive使用了递归算法，通过迭代器 MoveNext() 方法提取一个过滤器对象，执行其 OnActionExecuting 方法。 如果该方法设置了 filterContext.Cancel = true，则放弃后续执行代码。这种机制为我们提供了更好的控制，例如用它来实现伪静态页。一层一层调用所有的 ActionFilterAttribute.OnActionExecuting 方法，直到 MoveNext() == false。 在最后一次递归调用时，由于 enumerator.MoveNext() == false， _continuation() 方法被执行。这个就是前面给传递过来的 Action 方法委托，Action 方法总算是执行了。 在 Action 委托执行完成后，递归调逐级往上回溯，直到最初那个方法堆栈。这样所有ActionFilterAttribute.OnActionExecuted 也被执行完成。
到此开始进入最后的视图呈现阶段，可以把数据呈现到视图上，Controller 提供了几个重载的 RenderView() 来完成这个工作。
protected void RenderView(string viewName) { RenderView(viewName, String.Empty, ViewData); } protected void RenderView(string viewName, string masterName) { RenderView(viewName, masterName, ViewData); } protected void RenderView(string viewName, object viewData) { RenderView(viewName, String.Empty, viewData); } protected virtual void RenderView(string viewName, string masterName, object viewData) { ViewContext viewContext = new ViewContext(ControllerContext, viewName, masterName, viewData, TempData); ViewEngine.RenderView(viewContext); } 将一路传递过来的相关 "数据" (上下文)ControllerContext 再次包装成ViewContext 。当然，这次依然会多出些东西，里面就有我们向视图传递的数据 —— viewData 和tempData。作为默认选择，MVC 创建 WebForm 视图引擎来展示结果。其他的视图引擎可以去看mvccontrib，这个项目就是整合：Castle Windsor 、StructureMap 、Spring.NET 等IoC框架以及视图引擎，包括Castle MonoRail所用的NVelocityView视图引擎、NHamlView视图引擎、XsltViewEngine视图引擎等等。
继续看这个 WebFormViewEngine：
namespace System.Web.Mvc { using System; using System.Globalization; using System.Web.Compilation; using System.Web.Resources; using System.Web.Routing; using System.Web.Mvc.Resources; [AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)] public class WebFormViewEngine : IViewEngine { private IBuildManager _buildManager; private IViewLocator _viewLocator; internal IBuildManager BuildManager { get { if (_buildManager == null) { _buildManager = new BuildManagerWrapper(); } return _buildManager; } set { _buildManager = value; } } public IViewLocator ViewLocator { get { if (_viewLocator == null) { _viewLocator = new WebFormViewLocator(); } return _viewLocator; } set { _viewLocator = value; } } protected virtual void RenderView(ViewContext viewContext) { if (viewContext == null) { throw new ArgumentNullException("viewContext"); } string viewPath = ViewLocator.GetViewLocation(viewContext, viewContext.ViewName); if (String.IsNullOrEmpty(viewPath)) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.WebFormViewEngine_ViewNotFound, viewContext.ViewName)); } object viewInstance = BuildManager.CreateInstanceFromVirtualPath(viewPath, typeof(object)); if (viewInstance == null) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.WebFormViewEngine_ViewCouldNotBeCreated, viewPath)); } ViewPage viewPage = viewInstance as ViewPage; if (viewPage != null) { if (!String.IsNullOrEmpty(viewContext.MasterName)) { string masterLocation = ViewLocator.GetMasterLocation(viewContext, viewContext.MasterName); if (String.IsNullOrEmpty(masterLocation)) { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.WebFormViewEngine_MasterNotFound, viewContext.MasterName)); } // We don't set the page's MasterPageFile directly since it will get // overwritten by a statically-defined value. In ViewPage we wait until // the PreInit phase until we set the new value. viewPage.MasterLocation = masterLocation; } viewPage.SetViewData(viewContext.ViewData); viewPage.RenderView(viewContext); } else { ViewUserControl viewUserControl = viewInstance as ViewUserControl; if (viewUserControl != null) { if (!String.IsNullOrEmpty(viewContext.MasterName)) { throw new InvalidOperationException(MvcResources.WebFormViewEngine_UserControlCannotHaveMaster); } viewUserControl.SetViewData(viewContext.ViewData); viewUserControl.RenderView(viewContext); } else { throw new InvalidOperationException( String.Format( CultureInfo.CurrentUICulture, MvcResources.WebFormViewEngine_WrongViewBase, viewPath)); } } } IViewEngine Members }} 首先会创建一个 WebFormViewLocator 对象来获取视图存放路径。
namespace System.Web.Mvc {
public class WebFormViewLocator : ViewLocator {
public WebFormViewLocator() {
ViewLocationFormats = new[] {
"~/Views/{1}/{0}.aspx",
"~/Views/{1}/{0}.ascx",
"~/Views/Shared/{0}.aspx",
"~/Views/Shared/{0}.ascx"
};
MasterLocationFormats = new[] {
"~/Views/{1}/{0}.master",
"~/Views/Shared/{0}.master"
};
}
}
}
在获取路径后，WebFormViewEngine 通过一个包装类 BuildManagerWrapper 间接调用 System.Web.Compilation.BuildManager 的静态方法 CreateInstanceFromVirtualPath() 将视图进行编译，并返回一个对象实例。(System.Web.Compilation.BuildManager BuildManager 类管理应用程序的程序集和页的编译过程)，后面通过 as 转换结果来判断视图是 ViewPage 还是 ViewUserControl。ViewPage 继承自我们所熟悉的 System.Web.UI.Page，它的 RenderView() 方法也就是完成WebForm的 Page.ProcessRequest() 的处理而已，也就完成了对WebForm模型的置换。
下面看看ViewPage和ViewUserControl的代码：
namespace System.Web.Mvc {
using System.Web.UI;
[AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
[AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public class ViewPage : Page, IViewDataContainer {
private string _masterLocation;
private object _viewData;
public string MasterLocation {
get {
return _masterLocation ?? String.Empty;
}
set {
_masterLocation = value;
}
}
public AjaxHelper Ajax {
get;
set;
}
public HtmlHelper Html {
get;
set;
}
public TempDataDictionary TempData {
get {
return ViewContext.TempData;
}
}
public UrlHelper Url {
get;
set;
}
public ViewContext ViewContext {
get;
private set;
}
public ViewData ViewData {
get {
return new ViewData(_viewData);
}
}
public HtmlTextWriter Writer {
get;
private set;
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2109:ReviewVisibleEventHandlers")]
protected override void OnPreInit(EventArgs e) {
base.OnPreInit(e);
if (!String.IsNullOrEmpty(MasterLocation)) {
MasterPageFile = MasterLocation;
}
}
public virtual void RenderView(ViewContext viewContext) {
ViewContext = viewContext;
Ajax = new AjaxHelper(viewContext);
Html = new HtmlHelper(viewContext);
Url = new UrlHelper(viewContext);
ProcessRequest(HttpContext.Current);
}
protected override void Render(HtmlTextWriter writer) {
Writer = writer;
try {
base.Render(writer);
}
finally {
Writer = null;
}
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
Justification = "There is already a ViewData property and it has a slightly different meaning.")]
protected internal virtual void SetViewData(object viewData) {
_viewData = viewData;
}
#region IViewDataContainer Members
object IViewDataContainer.ViewData {
get {
return _viewData;
}
}
#endregion
}
}
namespace System.Web.Mvc {
using System.ComponentModel;
using System.Globalization;
using System.Web.Resources;
using System.Web.UI;
using System.Web.Mvc.Resources;
[AspNetHostingPermission(System.Security.Permissions.SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
[AspNetHostingPermission(System.Security.Permissions.SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public class ViewUserControl : UserControl, IViewDataContainer {
private string _viewDataKey;
private object _viewData;
public AjaxHelper Ajax {
get {
return ViewPage.Ajax;
}
}
public HtmlHelper Html {
get {
return ViewPage.Html;
}
}
public TempDataDictionary TempData {
get {
return ViewPage.TempData;
}
}
public UrlHelper Url {
get {
return ViewPage.Url;
}
}
public ViewData ViewData {
get {
EnsureViewData();
return new ViewData(_viewData);
}
}
public ViewContext ViewContext {
get {
return ViewPage.ViewContext;
}
}
[DefaultValue("")]
public string ViewDataKey {
get {
return _viewDataKey ?? String.Empty;
}
set {
_viewDataKey = value;
}
}
private ViewPage ViewPage {
get {
ViewPage viewPage = Page as ViewPage;
if (viewPage == null) {
throw new InvalidOperationException(String.Format(CultureInfo.CurrentUICulture, MvcResources.ViewUserControl_RequiresViewPage));
}
return viewPage;
}
}
public HtmlTextWriter Writer {
get {
return ViewPage.Writer;
}
}
private void EnsureViewData() {
// Get the ViewData for this ViewUserControl, optionally using the specified ViewDataKey
if (_viewData != null) {
return;
}
IViewDataContainer vdc = GetViewDataContainer(this);
if (vdc == null) {
throw new InvalidOperationException(
String.Format(
CultureInfo.CurrentUICulture,
MvcResources.ViewUserControl_RequiresViewDataProvider,
AppRelativeVirtualPath));
}
if (String.IsNullOrEmpty(ViewDataKey)) {
_viewData = vdc.ViewData;
}
else {
_viewData = DataBinder.Eval(vdc.ViewData, ViewDataKey);
}
}
private static IViewDataContainer GetViewDataContainer(Control control) {
// Walk up the control hierarchy until we find someone that implements IViewDataContainer
while (control != null) {
control = control.Parent;
IViewDataContainer vdc = control as IViewDataContainer;
if (vdc != null) {
return vdc;
}
}
return null;
}
public virtual void RenderView(ViewContext viewContext) {
// TODO: Remove this hack. Without it, the browser appears to always load cached output
viewContext.HttpContext.Response.Cache.SetExpires(DateTime.Now);
ViewUserControlContainerPage containerPage = new ViewUserControlContainerPage(this);
containerPage.RenderView(viewContext);
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
Justification = "There is already a ViewData property and it has a slightly different meaning.")]
protected internal virtual void SetViewData(object viewData) {
_viewData = viewData;
}
#region IViewDataContainer Members
object IViewDataContainer.ViewData {
get {
EnsureViewData();
return _viewData;
}
}
#endregion
private sealed class ViewUserControlContainerPage : ViewPage {
public ViewUserControlContainerPage(ViewUserControl userControl) {
Controls.Add(userControl);
}
}
}
}
以直接在 Controller 中 RenderView 一个用户控件(ViewUserControl)，asp.net mvc 会替我们创建了一个 "空白页" (ViewUserControlContainerPage )来装载这个控件RenderView(ViewUserControl) 有个限制，就是不能有 MasterPage。
private sealed class ViewUserControlContainerPage : ViewPage {
public ViewUserControlContainerPage(ViewUserControl userControl) {
Controls.Add(userControl);
}
}
我们从 UrlRoutingModule 开始，历经 MvcRouteHandler、MvcHandler、Controller、ActionFilterAttribute，直到最后的 ViewEngine、ViewPage.完成了整个ASP.NET MVC的生命周期探索。
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