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詳解ASP.NET MVC的整個生命週期

2021-08-23 19:01:16

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。我相信大家，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的生命週期嗎？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，希望大家多多包涵，當然，更希望大家能不靈賜教，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 也是通過擴充套件 IHttpModule 和 IHttpHandler 來實現的，都是基於 ASP.NET 的 HttpApplication 的管道處理模型擴充套件的，在這個層面來說，它們是一樣的。當然，大家不要擡槓，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 管道擴充套件的。ASP.NET WEB API 類似專人做專事，它的管道處理模型更高效，並且有了 Restfull 的概念。當然，大家如何向瞭解更細的內容，就需要看原始碼了。或再說回來，到了 NET CORE 時代，二者又融合管道了。

二、MVC生命週期詳述

1、我們既然要說 ASP.NET MVC的生命週期，為了給大家一個整體印象，俗話說，文不如圖，我就貼一張圖，按著箭頭走，相信大家也會不能理解。

2、上圖很簡單，大家按著箭頭走，也能理解的差不多。以下是按著我的理解，劃分了4個模組。

（1）、路由模組

RouteBase 是對路由規則的抽象，也就是說，一個 RouteBase 物件，也就代表了一個條 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。我們有了路由規則，一定會把這個規則存放在一個地方，這個地方儲存了很多路由規則，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 物件。

RouteCollection 就是路由集合，用於儲存路由規則物件，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組。當請求到達路由模組後，ASP.NET MVC 框架就會根據 RouteTable 中設定的路由模板來匹配當前請求以獲得對應的 Controller 和 Action 資訊。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設定。也就是說，設定過程是有順序的，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物件，該型別的範例是：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 物件，找到最終處理請求的 IHttpHandler 的物件，該型別是 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 建立模組

經過了路由模組，生成了 RouteData 路由資料，它包含了根據路由規則匹配的 Controller 和 Action。有了路由資料，需要有處理器來處理請求，這個任務就交給了 RouteData 的 RouteHandler 屬性，它的型別是 IRouteHandler，它的值就是MvcRouteHandler，MvcRouteHandler 呼叫 GetHttpHandler 獲取處理請求的 IHttpHandler 物件，在 MVC 框架中就是 MvcHandler，詳細程式碼如下：

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 呼叫 IHttpHandler 型別的呼叫 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);建立 IControllerFactory，並建立 IController 物件。
    try
    {
        controller.Execute(this.RequestContext);執行Controller，背後就是呼叫相應的 Action 方法。
    }
    finally
    {
        controllerFactory.ReleaseController(controller);
    }
}

核心處理請求的方法是ProcessRequestInit()，用於建立 IController 和 IControllerFactory 範例。IControllerFactory 的實際型別是：DefaultControllerFactory，該型別用於建立 IController  型別的範例。

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
        }));
    }
}

以上加紅的程式碼就是建立 IController 的範例的邏輯。IController 範例建立完成後，判斷是否實現了 IAsyncController 介面，如果是，就非同步執行 Controller 方法的呼叫，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; 判讀是否是需要非同步執行
    if (asyncController != null)非同步執行
    {
        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 執行模組，通過 ControllerActionInvoker 呼叫 InvokeAction() 執行其方法。Action 方法的執行也有2個版本，一個是非同步版本，一個是同步版本。由於 ActionInvoker 實現了 IAsyncActionInvoker 介面，所以也是以已方式執行。該型別是 AsyncControllerActionInvoker。

A、當Controller物件被建立之後，緊接著就會執行Controler 物件的 Execute()，其實背後就是呼叫 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，全域性的、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); 獲取方法執行引數。
                    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（預設是System.Web.Mvc.DefaultModelBinder），它會從http請求的引數中提取資料並實現型別轉換，資料校驗（例如是否必填，資料格式等）以及是否自動裝配到action方法的引數中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，目的是對存取使用者的認證。在MVC5之前，認證和授權都是通過authorization filter來實現的，但現在這2個操作就分開來了，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介面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方法中寫的程式碼了（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 執行模組。

A、在 ActionResult 執行前後，仍然會有一個filter（IResultFilter），同樣的，通過實現 IResultFilter 介面你可以客製化自己的過濾邏輯。

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 就是把處理的使用者請求結果返回。因此 ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult就是具體的返回型別。

C、上面的返回型別可以大致分為2類：ViewResult 和非ViewResult。對於需要生成html頁面給使用者端的劃到ViewResult，而其他的例如返回文字，json資料等則劃分到非ViewResult，對於非ViewResult直接返回就可以了。

View的初始化和渲染呈現

A、對於 ViewResult 最終是由合適的 View Engine 通過呼叫 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 預設提供 WebForm（.aspx）和 Razor(.cshtml) 模板引擎，你可以通過實現 IViewEngine 介面來實現自己的 ViewEngine，然後在Application_Start方法中做如下注冊：

 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 標籤，基於AJAX的 form 等等。

（5）、作為總結，將每個節點主要的程式碼類貼出來。

這就是整個流程的程式碼節點，有些是同步執行，有些是非同步執行，把握關鍵點，我這裡只是謝了一個大概。

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

今天就到這裡了，東西雖然不多，但是也寫了2個多小時。今天就算自己有學習了一邊，大家一定要好好的把握這個流程，對於解決程式中的問題，擴充套件框架都有很大的好處。我們作為程式設計師的，應該要知道其一，也要知道其二。沒事，看看原始碼，我們對框架和我們自己的程式碼有更深的瞭解。當然，這樣做也是有代價的，需要更多的時間去支援，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的整個生命週期的文章就介紹到這了,更多相關ASP.NET MVC 生命週期內容請搜尋it145.com以前的文章或繼續瀏覽下面的相關文章希望大家以後多多支援it145.com！


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