詳解ASP.NET MVC的整個生命周期
一、介紹
我們做開發的，尤其是做微軟技術棧的，有一個方向是跳不過去的，那就是MVC開發。我相信大傢，做ASP.NET MVC 開發有的有很長時間，當然，也有剛進入這個行業的。無論如何，如果有人問你，你知道ASP.NET MVC的生命周期嗎？你知道它的來世今生嗎？你知道它和 ASP.NET WEBFORM 有什麼區別嗎?估計，這些問題，有很多人會答不上來，或者說不清楚。今天，我就把我的理解寫出來，也是對我自己學習的一次回顧和總結吧。當然，由於本人能力有限，在寫的過程中也可能會有一些錯誤，希望大傢多多包涵，當然，更希望大傢能不靈賜教，我們共同進步。
在開始之前，我們先來說說，ASP.NET Web Form 和 Asp.net MVC 有什麼區別，這裡說的區別，當然是本質區別，不是適用語法那個層次的。其實，說起來，ASP.NET WEB FORM 和 ASP.NET MVC 它們兩個沒有本質區別，使用的都是ASP.NET WEB FORM 的管道處理模型，ASP.NET MVC 也是通過擴展 IHttpModule 和 IHttpHandler 來實現的，都是基於 ASP.NET 的 HttpApplication 的管道處理模型擴展的，在這個層面來說，它們是一樣的。當然，大傢不要抬杠，我說的本質區別都是在這個方面，不同意的勿噴。
有人會問，ASP.NET MVC 和 ASP.NET WEBAPI 它們會有什麼不同嗎？好像 WebAPi 能做的，WebMVC都可以完成，第一眼看上去，好像是這樣，但是它們有著本質的不同。WebAPI 的處理管道是重新寫過的，不是基於 HTTPApplication 管道擴展的。ASP.NET WEB API 類似專人做專事，它的管道處理模型更高效，並且有瞭 Restfull 的概念。當然，大傢如何向瞭解更細的內容，就需要看源碼瞭。或再說回來，到瞭 NET CORE 時代，二者又融合管道瞭。
二、MVC生命周期詳述
1、我們既然要說 ASP.NET MVC的生命周期，為瞭給大傢一個整體印象，俗話說，文不如圖，我就貼一張圖，按著箭頭走，相信大傢也會不能理解。
2、上圖很簡單，大傢按著箭頭走，也能理解的差不多。以下是按著我的理解，劃分瞭4個模塊。
（1）、路由模塊
RouteBase 是對路由規則的抽象，也就是說，一個 RouteBase 對象，也就代表瞭一個條 路由規則。在 ASP.NET MVC 中，有一個唯一的子類實現就是 Route ，它同樣也是路由規則的代表。我們有瞭路由規則，一定會把這個規則存放在一個地方，這個地方保存瞭很多路由規則，這個地方就是 RouteCollection，中文叫“路由集合”，因為這個集合裡面包含的就是 RouteBase 對象。
RouteCollection 就是路由集合，用於保存路由規則對象，它的定義形式：
[TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
public class RouteCollection : Collection<RouteBase>
{
private class ReadLockDisposable : IDisposable
{
private ReaderWriterLockSlim _rwLock;
public ReadLockDisposable(ReaderWriterLockSlim rwLock)
{
this._rwLock = rwLock;
}
void IDisposable.Dispose()
{
this._rwLock.ExitReadLock();
}
}
......
RouteTable 就是路由表，其實它和 RouteCollection 是一樣的。
public class RouteTable
{
private static RouteCollection _instance = new RouteCollection();
public static RouteCollection Routes
{
get
{
return RouteTable._instance;
}
}
}
在ASP.NET MVC處理管線中的第一站就是路由模塊。當請求到達路由模塊後，ASP.NET MVC 框架就會根據 RouteTable 中配置的路由模板來匹配當前請求以獲得對應的 Controller 和 Action 信息。具體的匹配過程就是有UrlRoutingModule(System.Web.Routing.UrlRoutingModule)來實現的。如果遇到一個匹配的規則，就會立刻跳出下面的配置。也就是說，配置過程是有順序的，如果有一個匹配，後面就算有匹配的也不會執行的。
namespace System.Web.Routing
{
[TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
public class UrlRoutingModule : IHttpModule
{
private static readonly object _contextKey = new object();
private static readonly object _requestDataKey = new object();
private RouteCollection _routeCollection;
public RouteCollection RouteCollection
{
get
{
if (this._routeCollection == null)
{
this._routeCollection = RouteTable.Routes;
}
return this._routeCollection;
}
set
{
this._routeCollection = value;
}
}
protected virtual void Dispose()
{
}
protected virtual void Init(HttpApplication application)
{
if (application.Context.Items[UrlRoutingModule._contextKey] != null)
{
return;
}
application.Context.Items[UrlRoutingModule._contextKey] = UrlRoutingModule._contextKey;
application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);
}
private void OnApplicationPostResolveRequestCache(object sender, EventArgs e)
{
HttpApplication httpApplication = (HttpApplication)sender;
HttpContextBase context = new HttpContextWrapper(httpApplication.Context);
this.PostResolveRequestCache(context);
}
[Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")]
public virtual void PostMapRequestHandler(HttpContextBase context)
{
}
public virtual void PostResolveRequestCache(HttpContextBase context)
{
RouteData routeData = this.RouteCollection.GetRouteData(context); 第一步匹配路由規則
if (routeData == null)
{
return;
}
IRouteHandler routeHandler = routeData.RouteHandler; 第二步：如有匹配，就找到RouteHandler對象，該類型的實例是：MvcRouteHandler。
if (routeHandler == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
}
if (routeHandler is StopRoutingHandler)
{
return;
}
RequestContext requestContext = new RequestContext(context, routeData);
context.Request.RequestContext = requestContext;
IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);第三步，根據 RouteHandler 對象，找到最終處理請求的 IHttpHandler 的對象，該類型是 MvcHandler
if (httpHandler == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[]
{
routeHandler.GetType()
}));
}
if (!(httpHandler is UrlAuthFailureHandler))
{
context.RemapHandler(httpHandler);第四步，有找到的 IHttpHandler 處理請求。
return;
}
if (FormsAuthenticationModule.FormsAuthRequired)
{
UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
return;
}
throw new HttpException(401, SR.GetString("Assess_Denied_Description3"));
}
void IHttpModule.Dispose()
{
this.Dispose();
}
void IHttpModule.Init(HttpApplication application)
{
this.Init(application);
}
}
}
（2）、Controller 創建模塊
經過瞭路由模塊，生成瞭 RouteData 路由數據，它包含瞭根據路由規則匹配的 Controller 和 Action。有瞭路由數據，需要有處理器來處理請求，這個任務就交給瞭 RouteData 的 RouteHandler 屬性，它的類型是 IRouteHandler，它的值就是MvcRouteHandler，MvcRouteHandler 調用 GetHttpHandler 獲取處理請求的 IHttpHandler 對象，在 MVC 框架中就是 MvcHandler，詳細代碼如下：
namespace System.Web.Mvc
{
/// <summary>Selects the controller that will handle an HTTP request.</summary>
public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState
{
private struct ProcessRequestState
{
internal IAsyncController AsyncController;
internal IControllerFactory Factory;
internal RequestContext RequestContext;
internal void ReleaseController()
{
this.Factory.ReleaseController(this.AsyncController);
}
}
[CompilerGenerated]
[Serializable]
private sealed class <>c
{
public static readonly MvcHandler.<>c <>9 = new MvcHandler.<>c();
public static BeginInvokeDelegate<MvcHandler.ProcessRequestState> <>9__20_0;
public static EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> <>9__20_1;
public static Func<KeyValuePair<string, object>, bool> <>9__26_0;
internal IAsyncResult <BeginProcessRequest>b__20_0(AsyncCallback asyncCallback, object asyncState, MvcHandler.ProcessRequestState innerState)
{
IAsyncResult result;
try
{
result = innerState.AsyncController.BeginExecute(innerState.RequestContext, asyncCallback, asyncState);
}
catch
{
innerState.ReleaseController();
throw;
}
return result;
}
internal void <BeginProcessRequest>b__20_1(IAsyncResult asyncResult, MvcHandler.ProcessRequestState innerState)
{
try
{
innerState.AsyncController.EndExecute(asyncResult);
}
finally
{
innerState.ReleaseController();
}
}
internal bool <RemoveOptionalRoutingParameters>b__26_0(KeyValuePair<string, object> entry)
{
return entry.Value == UrlParameter.Optional;
}
}
private static readonly object _processRequestTag = new object();
internal static readonly string MvcVersion = MvcHandler.GetMvcVersionString();
/// <summary>Contains the header name of the ASP.NET MVC version.</summary>
public static readonly string MvcVersionHeaderName = "X-AspNetMvc-Version";
private ControllerBuilder _controllerBuilder;
internal ControllerBuilder ControllerBuilder
{
get
{
if (this._controllerBuilder == null)
{
this._controllerBuilder = ControllerBuilder.Current;
}
return this._controllerBuilder;
}
set
{
this._controllerBuilder = value;
}
}
/// <summary>Gets or sets a value that indicates whether the MVC response header is disabled.</summary>
/// <returns>true if the MVC response header is disabled; otherwise, false.</returns>
public static bool DisableMvcResponseHeader
{
get;
set;
}
/// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary>
/// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns>
protected virtual bool IsReusable
{
get
{
return false;
}
}
/// <summary>Gets the request context.</summary>
/// <returns>The request context.</returns>
public RequestContext RequestContext
{
get;
private set;
}
/// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary>
/// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns>
bool IHttpHandler.IsReusable
{
get
{
return this.IsReusable;
}
}
/// <summary>Initializes a new instance of the <see cref="T:System.Web.Mvc.MvcHandler" /> class.</summary>
/// <param name="requestContext">The request context.</param>
/// <exception cref="T:System.ArgumentNullException">The <paramref name="requestContext" /> parameter is null.</exception>
public MvcHandler(RequestContext requestContext)
{
if (requestContext == null)
{
throw new ArgumentNullException("requestContext");
}
this.RequestContext = requestContext;
}
/// <summary>Adds the version header by using the specified HTTP context.</summary>
/// <param name="httpContext">The HTTP context.</param>
protected internal virtual void AddVersionHeader(HttpContextBase httpContext)
{
if (!MvcHandler.DisableMvcResponseHeader)
{
httpContext.Response.AppendHeader(MvcHandler.MvcVersionHeaderName, MvcHandler.MvcVersion);
}
}
/// <summary>Called by ASP.NET to begin asynchronous request processing.</summary>
/// <returns>The status of the asynchronous call.</returns>
/// <param name="httpContext">The HTTP context.</param>
/// <param name="callback">The asynchronous callback method.</param>
/// <param name="state">The state of the asynchronous object.</param>
protected virtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state)
{
HttpContextBase httpContext2 = new HttpContextWrapper(httpContext);
return this.BeginProcessRequest(httpContext2, callback, state);
}
/// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary>
/// <returns>The status of the asynchronous call.</returns>
/// <param name="httpContext">The HTTP context.</param>
/// <param name="callback">The asynchronous callback method.</param>
/// <param name="state">The state of the asynchronous object.</param>
protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state)
{
IController controller;
IControllerFactory factory;
this.ProcessRequestInit(httpContext, out controller, out factory);
IAsyncController asyncController = controller as IAsyncController;
if (asyncController != null)
{
BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0;
if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null)
{
arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0));
}
BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0;
EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0;
if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null)
{
arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1));
}
EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0;
MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState
{
AsyncController = asyncController,
Factory = factory,
RequestContext = this.RequestContext
};
SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext();
return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext);
}
Action action = delegate
{
try
{
controller.Execute(this.RequestContext);
}
finally
{
factory.ReleaseController(controller);
}
};
return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag);
}
/// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary>
/// <param name="asyncResult">The asynchronous result.</param>
protected internal virtual void EndProcessRequest(IAsyncResult asyncResult)
{
AsyncResultWrapper.End(asyncResult, MvcHandler._processRequestTag);
}
private static string GetMvcVersionString()
{
return new AssemblyName(typeof(MvcHandler).Assembly.FullName).Version.ToString(2);
}
/// <summary>Processes the request by using the specified HTTP request context.</summary>
/// <param name="httpContext">The HTTP context.</param>
protected virtual void ProcessRequest(HttpContext httpContext)
{
HttpContextBase httpContext2 = new HttpContextWrapper(httpContext);
this.ProcessRequest(httpContext2);
}
/// <summary>Processes the request by using the specified base HTTP request context.</summary>
/// <param name="httpContext">The HTTP context.</param>
protected internal virtual void ProcessRequest(HttpContextBase httpContext)
{
IController controller;
IControllerFactory controllerFactory;
this.ProcessRequestInit(httpContext, out controller, out controllerFactory);
try
{
controller.Execute(this.RequestContext);
}
finally
{
controllerFactory.ReleaseController(controller);
}
}
private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
{
HttpContext current = HttpContext.Current;
if (current != null)
{
bool? flag = ValidationUtility.IsValidationEnabled(current);
bool flag2 = true;
if (flag.GetValueOrDefault() == flag2 & flag.HasValue)
{
ValidationUtility.EnableDynamicValidation(current);
}
}
this.AddVersionHeader(httpContext);
this.RemoveOptionalRoutingParameters();
string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
factory = this.ControllerBuilder.GetControllerFactory();
controller = factory.CreateController(this.RequestContext, requiredString);
if (controller == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[]
{
factory.GetType(),
requiredString
}));
}
}
private void RemoveOptionalRoutingParameters()
{
IDictionary<string, object> arg_2F_0 = this.RequestContext.RouteData.Values;
Func<KeyValuePair<string, object>, bool> arg_2F_1;
if ((arg_2F_1 = MvcHandler.<>c.<>9__26_0) == null)
{
arg_2F_1 = (MvcHandler.<>c.<>9__26_0 = new Func<KeyValuePair<string, object>, bool>(MvcHandler.<>c.<>9.<RemoveOptionalRoutingParameters>b__26_0));
}
arg_2F_0.RemoveFromDictionary(arg_2F_1);
}
/// <summary>Enables processing of HTTP Web requests by a custom HTTP handler that implements the <see cref="T:System.Web.IHttpHandler" /> interface.</summary>
/// <param name="httpContext">An <see cref="T:System.Web.HttpContext" /> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) that are used to service HTTP requests.</param>
void IHttpHandler.ProcessRequest(HttpContext httpContext)
{
this.ProcessRequest(httpContext);
}
/// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary>
/// <returns>The status of the asynchronous call.</returns>
/// <param name="context">The HTTP context.</param>
/// <param name="cb">The asynchronous callback method.</param>
/// <param name="extraData">The data.</param>
IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
{
return this.BeginProcessRequest(context, cb, extraData);
}
/// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary>
/// <param name="result">The asynchronous result.</param>
void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
{
this.EndProcessRequest(result);
}
}
}
HttpRuntime 調用 IHttpHandler 類型的調用 ProcessRequest() 方法，用於處理請求。
protected internal virtual void ProcessRequest(HttpContextBase httpContext)
{
IController controller;
IControllerFactory controllerFactory;
this.ProcessRequestInit(httpContext, out controller, out controllerFactory);創建 IControllerFactory，並創建 IController 對象。
try
{
controller.Execute(this.RequestContext);執行Controller，背後就是調用相應的 Action 方法。
}
finally
{
controllerFactory.ReleaseController(controller);
}
}
核心處理請求的方法是ProcessRequestInit()，用於創建 IController 和 IControllerFactory 實例。IControllerFactory 的實際類型是：DefaultControllerFactory，該類型用於創建 IController 類型的實例。
private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
{
HttpContext current = HttpContext.Current;
if (current != null)
{
bool? flag = ValidationUtility.IsValidationEnabled(current);
bool flag2 = true;
if (flag.GetValueOrDefault() == flag2 & flag.HasValue)
{
ValidationUtility.EnableDynamicValidation(current);
}
}
this.AddVersionHeader(httpContext);
this.RemoveOptionalRoutingParameters();
string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
factory = this.ControllerBuilder.GetControllerFactory();
controller = factory.CreateController(this.RequestContext, requiredString);
if (controller == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[]
{
factory.GetType(),
requiredString
}));
}
}
以上加紅的代碼就是創建 IController 的實例的邏輯。IController 實例創建完成後，判斷是否實現瞭 IAsyncController 接口，如果是，就異步執行 Controller 方法的調用，否則就同步執行。
protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state)
{
IController controller;
IControllerFactory factory;
this.ProcessRequestInit(httpContext, out controller, out factory);
IAsyncController asyncController = controller as IAsyncController; 判讀是否是需要異步執行
if (asyncController != null)異步執行
{
BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0;
if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null)
{
arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0));
}
BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0;
EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0;
if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null)
{
arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1));
}
EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0;
MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState
{
AsyncController = asyncController,
Factory = factory,
RequestContext = this.RequestContext
};
SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext();
return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext);
}
Action action = delegate//同步執行。
{
try
{
controller.Execute(this.RequestContext);
}
finally
{
factory.ReleaseController(controller);
}
};
return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag);
}
（3）、Action 執行模塊，通過 ControllerActionInvoker 調用 InvokeAction() 執行其方法。Action 方法的執行也有2個版本，一個是異步版本，一個是同步版本。由於 ActionInvoker 實現瞭 IAsyncActionInvoker 接口，所以也是以已方式執行。該類型是 AsyncControllerActionInvoker。
A、當Controller對象被創建之後，緊接著就會執行Controler 對象的 Execute()，其實背後就是調用 InvokeAction() 方法：
public virtual bool InvokeAction(ControllerContext controllerContext, string actionName)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
if (string.IsNullOrEmpty(actionName) && !controllerContext.RouteData.HasDirectRouteMatch())
{
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName");
}
ControllerDescriptor controllerDescriptor = this.GetControllerDescriptor(controllerContext);
ActionDescriptor actionDescriptor = this.FindAction(controllerContext, controllerDescriptor, actionName);
if (actionDescriptor != null)
{
FilterInfo filters = this.GetFilters(controllerContext, actionDescriptor); 獲取所有過濾器，全局的、控制器的和方法的
try
{
AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);認證過濾器的執行。
if (authenticationContext.Result != null)
{
AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result);
this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result);
}
else
{
AuthorizationContext authorizationContext = this.InvokeAuthorizationFilters(controllerContext, filters.AuthorizationFilters, actionDescriptor);授權過濾器的執行。
if (authorizationContext.Result != null)
{
AuthenticationChallengeContext authenticationChallengeContext2 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authorizationContext.Result);
this.InvokeActionResult(controllerContext, authenticationChallengeContext2.Result ?? authorizationContext.Result);
}
else
{
if (controllerContext.Controller.ValidateRequest)
{
ControllerActionInvoker.ValidateRequest(controllerContext);
}
IDictionary<string, object> parameterValues = this.GetParameterValues(controllerContext, actionDescriptor); 獲取方法執行參數。
ActionExecutedContext actionExecutedContext = this.InvokeActionMethodWithFilters(controllerContext, filters.ActionFilters, actionDescriptor, parameterValues); 執行action，同時執行執行方法前後的 IAcctionFilter
AuthenticationChallengeContext authenticationChallengeContext3 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, actionExecutedContext.Result);
this.InvokeActionResultWithFilters(controllerContext, filters.ResultFilters, authenticationChallengeContext3.Result ?? actionExecutedContext.Result); 執行 ActionResult，同時執行方法前後的 IResultFilter
}
}
}
catch (ThreadAbortException)
{
throw;
}
catch (Exception exception)
{
ExceptionContext exceptionContext = this.InvokeExceptionFilters(controllerContext, filters.ExceptionFilters, exception);
if (!exceptionContext.ExceptionHandled)
{
throw;
}
this.InvokeActionResult(controllerContext, exceptionContext.Result);//異常過濾器的執行。
}
return true;
}
return false;
}
B、當選擇完合適的Action後，接著就是 ModelBinder（默認是System.Web.Mvc.DefaultModelBinder），它會從http請求的參數中提取數據並實現類型轉換，數據校驗（例如是否必填，數據格式等）以及是否自動裝配到action方法的參數中System.Web.Mvc.DefaultModelBinder
protected virtual IDictionary<string, object> GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
{
Dictionary<string, object> dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
ParameterDescriptor[] parameters = actionDescriptor.GetParameters();
for (int i = 0; i < parameters.Length; i++)
{
ParameterDescriptor parameterDescriptor = parameters[i];
dictionary[parameterDescriptor.ParameterName] = this.GetParameterValue(controllerContext, parameterDescriptor);
}
return dictionary;
}
protected virtual object GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor)
{
Type parameterType = parameterDescriptor.ParameterType;
IModelBinder arg_92_0 = this.GetModelBinder(parameterDescriptor);
IValueProvider valueProvider = controllerContext.Controller.ValueProvider;
string modelName = parameterDescriptor.BindingInfo.Prefix ?? parameterDescriptor.ParameterName;
Predicate<string> propertyFilter = ControllerActionInvoker.GetPropertyFilter(parameterDescriptor);
ModelBindingContext bindingContext = new ModelBindingContext
{
FallbackToEmptyPrefix = parameterDescriptor.BindingInfo.Prefix == null,
ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, parameterType),
ModelName = modelName,
ModelState = controllerContext.Controller.ViewData.ModelState,
PropertyFilter = propertyFilter,
ValueProvider = valueProvider
};
return arg_92_0.BindModel(controllerContext, bindingContext) ?? parameterDescriptor.DefaultValue;
}
C、Authentication Filter是mvc5中新增的一個Filter，它會先於authorization filter執行，目的是對訪問用戶的認證。在MVC5之前，認證和授權都是通過authorization filter來實現的，但現在這2個操作就分開來瞭，各自管各自嘍。
AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);
if (authenticationContext.Result != null)
{
AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result);
this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result);
}
D、Action filters有2個方法OnActionExecuting和OnActionExecuted分別在action執行前後執行。我們也可以通過實現IActionFilter接口來實現你個性化的過濾機制
protected virtual ActionExecutedContext InvokeActionMethodWithFilters(ControllerContext controllerContext, IList<IActionFilter> filters, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters)
{
ActionExecutingContext preContext = new ActionExecutingContext(controllerContext, actionDescriptor, parameters);
Func<ActionExecutedContext> seed = () => new ActionExecutedContext(controllerContext, actionDescriptor, false, null)
{
Result = this.InvokeActionMethod(controllerContext, actionDescriptor, parameters)
};
return filters.Reverse<IActionFilter>().Aggregate(seed, (Func<ActionExecutedContext> next, IActionFilter filter) => () => ControllerActionInvoker.InvokeActionMethodFilter(filter, preContext, next))();
}
E、接下來就是執行我們平時在Action方法中寫的代碼瞭（根據請求相應結果）
protected virtual ActionResult InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters)
{
object actionReturnValue = actionDescriptor.Execute(controllerContext, parameters);
return this.CreateActionResult(controllerContext, actionDescriptor, actionReturnValue);
}
（4）、ActionResult 執行模塊。
A、在 ActionResult 執行前後，仍然會有一個filter（IResultFilter），同樣的，通過實現 IResultFilter 接口你可以定制自己的過濾邏輯。
namespace System.Web.Mvc
{
/// <summary>Defines the methods that are required for a result filter.</summary>
public interface IResultFilter
{
/// <summary>Called before an action result executes.</summary>
/// <param name="filterContext">The filter context.</param>
void OnResultExecuting(ResultExecutingContext filterContext);
/// <summary>Called after an action result executes.</summary>
/// <param name="filterContext">The filter context.</param>
void OnResultExecuted(ResultExecutedContext filterContext);
}
}
B、ActionResult 就是把處理的用戶請求結果返回。因此 ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult就是具體的返回類型。
C、上面的返回類型可以大致分為2類：ViewResult 和非ViewResult。對於需要生成html頁面給客戶端的劃到ViewResult，而其他的例如返回文本，json數據等則劃分到非ViewResult，對於非ViewResult直接返回就可以瞭。
View的初始化和渲染呈現
A、對於 ViewResult 最終是由合適的 View Engine 通過調用 IView 的 Render() 方法來渲染的：
namespace System.Web.Mvc
{
/// <summary>Defines the methods that are required for a view engine.</summary>
public interface IViewEngine
{
/// <summary>Finds the specified partial view by using the specified controller context.</summary>
/// <returns>The partial view.</returns>
/// <param name="controllerContext">The controller context.</param>
/// <param name="partialViewName">The name of the partial view.</param>
/// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param>
ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache);
/// <summary>Finds the specified view by using the specified controller context.</summary>
/// <returns>The page view.</returns>
/// <param name="controllerContext">The controller context.</param>
/// <param name="viewName">The name of the view.</param>
/// <param name="masterName">The name of the master.</param>
/// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param>
ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache);
/// <summary>Releases the specified view by using the specified controller context.</summary>
/// <param name="controllerContext">The controller context.</param>
/// <param name="view">The view.</param>
void ReleaseView(ControllerContext controllerContext, IView view);
}
}
namespace System.Web.Mvc
{
/// <summary>Defines the methods that are required for a view.</summary>
public interface IView
{
/// <summary>Renders the specified view context by using the specified the writer object.</summary>
/// <param name="viewContext">The view context.</param>
/// <param name="writer">The writer object.</param>
void Render(ViewContext viewContext, TextWriter writer);
}
}
B、整個處理過程是由 IViewEngine 來實現的。ASP.NET MVC 默認提供 WebForm（.aspx）和 Razor(.cshtml) 模板引擎，你可以通過實現 IViewEngine 接口來實現自己的 ViewEngine，然後在Application_Start方法中做如下註冊：
protected void Application_Start()
{
//移除所有的View引擎包括Webform和Razor
ViewEngines.Engines.Clear();
//註冊你自己的View引擎
ViewEngines.Engines.Add(new CustomViewEngine());
}
C、最後，Html Helpers將幫我們生成 input 標簽，基於AJAX的 form 等等。
（5）、作為總結，將每個節點主要的代碼類貼出來。
這就是整個流程的代碼節點，有些是同步執行，有些是異步執行，把握關鍵點，我這裡隻是謝瞭一個大概。
UrlRoutingModule—–RouteCollection.GetRouteData(context)—–>IRouteHandler routeHandler = routeData.RouteHandler——》IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext)—–》context.RemapHandler(httpHandler)——->MvcHandler——->ProcessRequest()——>ProcessRequestInit()——–》IController——>controller.Execute(this.RequestContext)——–>ControllerActionInvoker——->InvoleAction()———>InvoleActionMethod()——->InvoleActionReslt()
三、結束
今天就到這裡瞭，東西雖然不多，但是也寫瞭2個多小時。今天就算自己有學習瞭一邊，大傢一定要好好的把握這個流程，對於解決程序中的問題，擴展框架都有很大的好處。我們作為程序員的，應該要知道其一，也要知道其二。沒事，看看源碼，我們對框架和我們自己的代碼有更深的瞭解。當然，這樣做也是有代價的，需要更多的時間去支持，我相信我們的付出是值得。不忘初心，繼續努力。老天不會辜負努力的人。
到此這篇關於詳解ASP.NET MVC的整個生命周期的文章就介紹到這瞭,更多相關ASP.NET MVC 生命周期內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet！
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