Asp.Net请求处理机制中IsApiRuntime解析

public int ProcessRequest(IntPtr ecb, int iWRType)
        {
            IntPtr intPtr = IntPtr.Zero;
            if (iWRType == 2)
            {
                intPtr = ecb;
                ecb = UnsafeNativeMethods.GetEcb(intPtr);
            }
            //首先创建ISAPIWorkerRequest，将请求报文封装在内，调用CreateWorkerRequest方法来实现，
            ISAPIWorkerRequest iSAPIWorkerRequest = null;
            int result;
            try
            {
                bool useOOP = iWRType == 1;
                iSAPIWorkerRequest = ISAPIWorkerRequest.CreateWorkerRequest(ecb, useOOP);
                iSAPIWorkerRequest.Initialize();
                string appPathTranslated = iSAPIWorkerRequest.GetAppPathTranslated();
                string appDomainAppPathInternal = HttpRuntime.AppDomainAppPathInternal;
                if (appDomainAppPathInternal == null || StringUtil.EqualsIgnoreCase(appPathTranslated, appDomainAppPathInternal))
                {
                    //调用ProcessRequestNoDemand方法，并将封装的请求报文传入进去
                    HttpRuntime.ProcessRequestNoDemand(iSAPIWorkerRequest);
                    result = 0;
                }
                else
                {
                    HttpRuntime.ShutdownAppDomain(ApplicationShutdownReason.PhysicalApplicationPathChanged, SR.GetString("Hosting_Phys_Path_Changed", new object[]
                    {
                        appDomainAppPathInternal,
                        appPathTranslated
                    }));
                    result = 1;
                }
            }
            catch (Exception ex)
            {
                try
                {
                    WebBaseEvent.RaiseRuntimeError(ex, this);
                }
                catch
                {
                }
                if (iSAPIWorkerRequest == null || !(iSAPIWorkerRequest.Ecb == IntPtr.Zero))
                {
                    throw;
                }
                if (intPtr != IntPtr.Zero)
                {
                    UnsafeNativeMethods.SetDoneWithSessionCalled(intPtr);
                }
                if (ex is ThreadAbortException)
                {
                    Thread.ResetAbort();
                }
                result = 0;
            }
            return result;
        }

在CreateWorkerRequest内部，根据不同的IIS版本创建不同的对象

// System.Web.Hosting.ISAPIWorkerRequest

internal static ISAPIWorkerRequest CreateWorkerRequest(IntPtr ecb, bool useOOP)

{
    ISAPIWorkerRequest result;
    if (useOOP)
    {
        EtwTrace.TraceEnableCheck(EtwTraceConfigType.DOWNLEVEL, IntPtr.Zero);
        if (EtwTrace.IsTraceEnabled(5, 1))
        {
            EtwTrace.Trace(EtwTraceType.ETW_TYPE_APPDOMAIN_ENTER, ecb, Thread.GetDomain().FriendlyName, null, false);
        }
        result = new ISAPIWorkerRequestOutOfProc(ecb);
    }
    else
    {
        int num = UnsafeNativeMethods.EcbGetVersion(ecb) >> 16;
        if (num >= 7)
        {
            EtwTrace.TraceEnableCheck(EtwTraceConfigType.IIS7_ISAPI, ecb);
        }
        else
        {
            EtwTrace.TraceEnableCheck(EtwTraceConfigType.DOWNLEVEL, IntPtr.Zero);
        }
        if (EtwTrace.IsTraceEnabled(5, 1))
        {
            EtwTrace.Trace(EtwTraceType.ETW_TYPE_APPDOMAIN_ENTER, ecb, Thread.GetDomain().FriendlyName, null, true);
        }
        if (num >= 7)
        {
            result = new ISAPIWorkerRequestInProcForIIS7(ecb);
        }
        else
        {
            if (num == 6)
            {
                result = new ISAPIWorkerRequestInProcForIIS6(ecb);
            }
            else
            {
                result = new ISAPIWorkerRequestInProc(ecb);
            }
        }
    }
    return result;
}

// System.Web.HttpRuntime
internal static void ProcessRequestNoDemand(HttpWorkerRequest wr)
{
    RequestQueue requestQueue = HttpRuntime._theRuntime._requestQueue;
    wr.UpdateInitialCounters();
    if (requestQueue != null)
    {
        wr = requestQueue.GetRequestToExecute(wr);
    }
    if (wr != null)
    {
        HttpRuntime.CalculateWaitTimeAndUpdatePerfCounter(wr);
        wr.ResetStartTime();
       //调用ProcessRequestNow方法，并将封装的请求报文传入
        HttpRuntime.ProcessRequestNow(wr);
    }
}

// System.Web.HttpRuntime
internal static void ProcessRequestNow(HttpWorkerRequest wr)
{
    HttpRuntime._theRuntime.ProcessRequestInternal(wr);
}

// System.Web.HttpRuntime
private void ProcessRequestInternal(HttpWorkerRequest wr)
{
    Interlocked.Increment(ref this._activeRequestCount);
    if (this._disposingHttpRuntime)
    {
        try
        {
            wr.SendStatus(503, "Server Too Busy");
            wr.SendKnownResponseHeader(12, "text/html; charset=utf-8");
            byte[] bytes = Encoding.ASCII.GetBytes("<html><body>Server Too Busy</body></html>");
            byte[] expr_45 = bytes;
            wr.SendResponseFromMemory(expr_45, expr_45.Length);
            wr.FlushResponse(true);
            wr.EndOfRequest();
        }
        finally
        {
            Interlocked.Decrement(ref this._activeRequestCount);
        }
        return;
    }
    HttpContext httpContext;
    try
    {
    //根据请求报文创建HttpContext对象，如果创建出错误就会返回404 
     httpContext = new HttpContext(wr, false);
    }
    catch
    {
        try
        {
            wr.SendStatus(400, "Bad Request");
            wr.SendKnownResponseHeader(12, "text/html; charset=utf-8");
            byte[] bytes2 = Encoding.ASCII.GetBytes("<html><body>Bad Request</body></html>");
            byte[] expr_A5 = bytes2;
            wr.SendResponseFromMemory(expr_A5, expr_A5.Length);
            wr.FlushResponse(true);
            wr.EndOfRequest();
            return;
        }
        finally
        {
            Interlocked.Decrement(ref this._activeRequestCount);
        }
    }
    wr.SetEndOfSendNotification(this._asyncEndOfSendCallback, httpContext);
    HostingEnvironment.IncrementBusyCount();
    try
    {
        try
        {
            //将第一次请求设置为false
            this.EnsureFirstRequestInit(httpContext);
        }
        catch
        {
            if (!httpContext.Request.IsDebuggingRequest)
            {
                throw;
            }
        }
        //初始化Response
        httpContext.Response.InitResponseWriter();
        //根据HttpApplicationFactory创建Application实例
        IHttpHandler applicationInstance = HttpApplicationFactory.GetApplicationInstance(httpContext);
        if (applicationInstance == null)
        {
            throw new HttpException(SR.GetString("Unable_create_app_object"));
        }
        if (EtwTrace.IsTraceEnabled(5, 1))
        {
            EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, httpContext.WorkerRequest, applicationInstance.GetType().FullName, "Start");
        }
        if (applicationInstance is IHttpAsyncHandler)
        {
            IHttpAsyncHandler httpAsyncHandler = (IHttpAsyncHandler)applicationInstance;
            httpContext.AsyncAppHandler = httpAsyncHandler;
            httpAsyncHandler.BeginProcessRequest(httpContext, this._handlerCompletionCallback, httpContext);
        }
        else
        {
            applicationInstance.ProcessRequest(httpContext);
            this.FinishRequest(httpContext.WorkerRequest, httpContext, null);
        }
    }
    catch (Exception e)
    {
        httpContext.Response.InitResponseWriter();
        this.FinishRequest(wr, httpContext, e);
    }
}

// System.Web.HttpRuntime
private void EnsureFirstRequestInit(HttpContext context)
{
    if (this._beforeFirstRequest)
    {
        bool flag = false;
        try
        {
            Monitor.Enter(this, ref flag);
            if (this._beforeFirstRequest)
            {

               //设置第一次请求为false
                this._firstRequestStartTime = DateTime.UtcNow;
                this.FirstRequestInit(context);
                this._beforeFirstRequest = false;
                context.FirstRequest = true;
            }
        }
        finally
        {
            if (flag)
            {
                Monitor.Exit(this);
            }
        }
    }
}