asp.net Page事件处理管道

我们知道页面就是一个处理程序，里面的实现非常复杂，网上也有很多资料讲到asp.net的管道处理，有关page的事件处理也不少；这里我就page的事件处理结果如图：

这里的总结来至asp.net本质论。我们也知道page的处理都集中在一个ProcessRequest方法中，该方法最终主要还是调用ProcessRequestMain方法。其主要实现如下：

private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint)
{
    try
    {
        HttpContext context = this.Context;
        string str = null;
        if (includeStagesBeforeAsyncPoint)
        {
            if (this.IsInAspCompatMode)
            {
                AspCompatApplicationStep.OnPageStartSessionObjects();
            }
            if (this.PageAdapter != null)
            {
                this._requestValueCollection = this.PageAdapter.DeterminePostBackMode();
                if (this._requestValueCollection != null)
                {
                    this._unvalidatedRequestValueCollection = this.PageAdapter.DeterminePostBackModeUnvalidated();
                }
            }
            else
            {
                this._requestValueCollection = this.DeterminePostBackMode();
                if (this._requestValueCollection != null)
                {
                    this._unvalidatedRequestValueCollection = this.DeterminePostBackModeUnvalidated();
                }
            }
            string callbackControlID = string.Empty;
            if (this.DetermineIsExportingWebPart())
            {
                if (!RuntimeConfig.GetAppConfig().WebParts.EnableExport)
                {
                    throw new InvalidOperationException(SR.GetString("WebPartExportHandler_DisabledExportHandler"));
                }
                str = this.Request.QueryString["webPart"];
                if (string.IsNullOrEmpty(str))
                {
                    throw new InvalidOperationException(SR.GetString("WebPartExportHandler_InvalidArgument"));
                }
                if (string.Equals(this.Request.QueryString["scope"], "shared", StringComparison.OrdinalIgnoreCase))
                {
                    this._pageFlags.Set(4);
                }
                string str3 = this.Request.QueryString["query"];
                if (str3 == null)
                {
                    str3 = string.Empty;
                }
                this.Request.QueryStringText = str3;
                context.Trace.IsEnabled = false;
            }
            if (this._requestValueCollection != null)
            {
                if (this._requestValueCollection["__VIEWSTATEENCRYPTED"] != null)
                {
                    this.ContainsEncryptedViewState = true;
                }
                callbackControlID = this._requestValueCollection["__CALLBACKID"];
                if ((callbackControlID != null) && (this._request.HttpVerb == HttpVerb.POST))
                {
                    this._isCallback = true;
                }
                else if (!this.IsCrossPagePostBack)
                {
                    VirtualPath path = null;
                    if (this._requestValueCollection["__PREVIOUSPAGE"] != null)
                    {
                        try
                        {
                            path = VirtualPath.CreateNonRelativeAllowNull(DecryptString(this._requestValueCollection["__PREVIOUSPAGE"], Purpose.WebForms_Page_PreviousPageID));
                        }
                        catch
                        {
                            this._pageFlags[8] = true;
                        }
                        if ((path != null) && (path != this.Request.CurrentExecutionFilePathObject))
                        {
                            this._pageFlags[8] = true;
                            this._previousPagePath = path;
                        }
                    }
                }
            }
            if (this.MaintainScrollPositionOnPostBack)
            {
                this.LoadScrollPosition();
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin PreInit");
            }
            this.PerformPreInit();
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End PreInit");
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin Init");
            }
            this.InitRecursive(null);
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End Init");
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin InitComplete");
            }
            this.OnInitComplete(EventArgs.Empty);
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End InitComplete");
            }
            if (this.IsPostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin LoadState");
                }
                this.LoadAllState();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End LoadState");
                    this.Trace.Write("aspx.page", "Begin ProcessPostData");
                }
                this.ProcessPostData(this._requestValueCollection, true);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End ProcessPostData");
                }
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin PreLoad");
            }
            this.OnPreLoad(EventArgs.Empty);
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End PreLoad");
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin Load");
            }
            this.LoadRecursive();
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End Load");
            }
            if (this.IsPostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin ProcessPostData Second Try");
                }
                this.ProcessPostData(this._leftoverPostData, false);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End ProcessPostData Second Try");
                    this.Trace.Write("aspx.page", "Begin Raise ChangedEvents");
                }
                this.RaiseChangedEvents();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End Raise ChangedEvents");
                    this.Trace.Write("aspx.page", "Begin Raise PostBackEvent");
                }
                this.RaisePostBackEvent(this._requestValueCollection);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End Raise PostBackEvent");
                }
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin LoadComplete");
            }
            this.OnLoadComplete(EventArgs.Empty);
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End LoadComplete");
            }
            if (this.IsPostBack && this.IsCallback)
            {
                this.PrepareCallback(callbackControlID);
            }
            else if (!this.IsCrossPagePostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin PreRender");
                }
                this.PreRenderRecursiveInternal();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End PreRender");
                }
            }
        }
        if ((this._legacyAsyncInfo == null) || this._legacyAsyncInfo.CallerIsBlocking)
        {
            this.ExecuteRegisteredAsyncTasks();
        }
        this.ValidateRawUrlIfRequired();
        if (includeStagesAfterAsyncPoint)
        {
            if (this.IsCallback)
            {
                this.RenderCallback();
            }
            else if (!this.IsCrossPagePostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin PreRenderComplete");
                }
                this.PerformPreRenderComplete();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End PreRenderComplete");
                }
                if (context.TraceIsEnabled)
                {
                    this.BuildPageProfileTree(this.EnableViewState);
                    this.Trace.Write("aspx.page", "Begin SaveState");
                }
                this.SaveAllState();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End SaveState");
                    this.Trace.Write("aspx.page", "Begin SaveStateComplete");
                }
                this.OnSaveStateComplete(EventArgs.Empty);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End SaveStateComplete");
                    this.Trace.Write("aspx.page", "Begin Render");
                }
                if (str != null)
                {
                    this.ExportWebPart(str);
                }
                else
                {
                    this.RenderControl(this.CreateHtmlTextWriter(this.Response.Output));
                } 
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End Render");
                }
                this.CheckRemainingAsyncTasks(false);
            }
        }
    }  
    catch (ConfigurationException)
    {
        throw;
    }
     
}

在这个方法中有两段代码比较有意思

this.OnInitComplete(EventArgs.Empty);

if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End InitComplete");
            }
            if (this.IsPostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin LoadState");
                }
                this.LoadAllState();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End LoadState");
                    this.Trace.Write("aspx.page", "Begin ProcessPostData");
                }
                this.ProcessPostData(this._requestValueCollection, true);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End ProcessPostData");
                }
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin PreLoad");
            }
            this.OnPreLoad(EventArgs.Empty);

和

this.LoadRecursive();
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "End Load");
            }
            if (this.IsPostBack)
            {
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "Begin ProcessPostData Second Try");
                }
                this.ProcessPostData(this._leftoverPostData, false);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End ProcessPostData Second Try");
                    this.Trace.Write("aspx.page", "Begin Raise ChangedEvents");
                }
                this.RaiseChangedEvents();
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End Raise ChangedEvents");
                    this.Trace.Write("aspx.page", "Begin Raise PostBackEvent");
                }
                this.RaisePostBackEvent(this._requestValueCollection);
                if (context.TraceIsEnabled)
                {
                    this.Trace.Write("aspx.page", "End Raise PostBackEvent");
                }
            }
            if (context.TraceIsEnabled)
            {
                this.Trace.Write("aspx.page", "Begin LoadComplete");
            }
            this.OnLoadComplete(EventArgs.Empty);