PageAsyncTask.cs source code in C# .NET

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                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / xsp / System / Web / UI / PageAsyncTask.cs / 1305376 / PageAsyncTask.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI { 
 
using System;
using System.Collections; 
using System.Security;
using System.Security.Permissions;
using System.Threading;
using System.Web; 
using System.Web.UI;
using System.Web.Util; 
 
public sealed class PageAsyncTask {
    private BeginEventHandler   _beginHandler; 
    private EndEventHandler     _endHandler;
    private EndEventHandler     _timeoutHandler;
    private Object              _state;
    private bool                _executeInParallel; 

    private PageAsyncTaskManager _taskManager; 
    private int                 _completionMethodLock; 
    private bool                _started;
    private bool                _completed; 
    private bool                _completedSynchronously;
    private AsyncCallback       _completionCallback;
    private IAsyncResult        _asyncResult;
    private Exception           _error; 

    public PageAsyncTask(BeginEventHandler beginHandler, EndEventHandler endHandler, EndEventHandler timeoutHandler, Object state) 
        : this(beginHandler, endHandler, timeoutHandler, state, false) { 
    }
 
    public PageAsyncTask(BeginEventHandler beginHandler, EndEventHandler endHandler, EndEventHandler timeoutHandler, Object state, bool executeInParallel) {
        if (beginHandler == null) {
            throw new ArgumentNullException("beginHandler");
        } 
        if (endHandler == null) {
            throw new ArgumentNullException("endHandler"); 
        } 

        _beginHandler = beginHandler; 
        _endHandler = endHandler;
        _timeoutHandler = timeoutHandler;
        _state = state;
        _executeInParallel = executeInParallel; 
    }
 
    public BeginEventHandler BeginHandler { 
        get { return _beginHandler; }
    } 

    public EndEventHandler EndHandler {
        get { return _endHandler; }
    } 

    public EndEventHandler TimeoutHandler { 
        get { return _timeoutHandler; } 
    }
 
    public Object State {
        get { return _state; }
    }
 
    public bool ExecuteInParallel {
        get { return _executeInParallel; } 
    } 

    internal bool Started { 
        get { return _started; }
    }

    internal bool CompletedSynchronously { 
        get { return _completedSynchronously; }
    } 
 
    internal bool Completed {
        get { return _completed; } 
    }

    internal IAsyncResult AsyncResult {
        get { return _asyncResult; } 
    }
 
    internal Exception Error { 
        get { return _error; }
    } 

    internal void Start(PageAsyncTaskManager manager, Object source, EventArgs args) {
        Debug.Assert(!_started);
 
        _taskManager = manager;
        _completionCallback = new AsyncCallback(this.OnAsyncTaskCompletion); 
        _started = true; 

        Debug.Trace("Async", "Start task"); 

        try {
            IAsyncResult ar = _beginHandler(source, args, _completionCallback, _state);
 
            if (ar == null) {
                throw new InvalidOperationException(SR.GetString(SR.Async_null_asyncresult)); 
            } 

            if (_asyncResult == null) { 
                // _asyncResult could be not null if already completed
                _asyncResult = ar;
            }
        } 
        catch (Exception e) {
            Debug.Trace("Async", "Task failed to start"); 
 
            _error = e;
            _completed = true; 
            _completedSynchronously = true;
            _taskManager.TaskCompleted(true /*onCallerThread*/); // notify TaskManager
            // it is ok to say false (onCallerThread) above because this kind of
            // error completion will never be the last in ResumeTasks() 
        }
    } 
 
    private void OnAsyncTaskCompletion(IAsyncResult ar) {
        Debug.Trace("Async", "Task completed, CompletedSynchronously=" + ar.CompletedSynchronously); 

        if (_asyncResult == null) {
            // _asyncResult could be null if the code not yet returned from begin method
            _asyncResult = ar; 
        }
 
        CompleteTask(false /*timedOut*/); 
    }
 
    internal void ForceTimeout(bool syncCaller) {
        Debug.Trace("Async", "Task timed out");
        CompleteTask(true /*timedOut*/, syncCaller /*syncTimeoutCaller*/);
    } 

    private void CompleteTask(bool timedOut) { 
        CompleteTask(timedOut, false /*syncTimeoutCaller*/); 
    }
 
    private void CompleteTask(bool timedOut, bool syncTimeoutCaller) {
        if (Interlocked.Exchange(ref _completionMethodLock, 1) != 0) {
            return;
        } 

        bool needSetupThreadContext; 
        bool responseEnded = false; 

        if (timedOut) { 
            needSetupThreadContext = !syncTimeoutCaller;
        }
        else {
            _completedSynchronously = _asyncResult.CompletedSynchronously; 
            needSetupThreadContext = !_completedSynchronously;
        } 
 
        // call the completion or timeout handler
        //  when neeeded setup the thread context and lock 
        //  catch and remember all exceptions

        HttpApplication app = _taskManager.Application;
 
        try {
            if (needSetupThreadContext) { 
 
                lock (app) {
                    HttpApplication.ThreadContext threadContext = null; 
                    try {
                        threadContext = app.OnThreadEnter();
                        if (timedOut) {
                            if (_timeoutHandler != null) { 
                                _timeoutHandler(_asyncResult);
                            } 
                        } 
                        else {
                            _endHandler(_asyncResult); 
                        }
                    }
                    finally {
                        if (threadContext != null) { 
                            threadContext.Leave();
                        } 
                    } 
                }
            } 
            else {
                if (timedOut) {
                    if (_timeoutHandler != null) {
                        _timeoutHandler(_asyncResult); 
                    }
                } 
                else { 
                    _endHandler(_asyncResult);
                } 
            }
        }
        catch (ThreadAbortException e) {
           _error = e; 

           HttpApplication.CancelModuleException exceptionState = e.ExceptionState as HttpApplication.CancelModuleException; 
 
           // Is this from Response.End()
           if (exceptionState != null && !exceptionState.Timeout) { 
               // Mark the request as completed
               lock (app) {
                   // Handle response end once. Skip if already initiated (previous AsyncTask)
                   if (!app.IsRequestCompleted) { 
                       responseEnded = true;
                       app.CompleteRequest(); 
                   } 
               }
 
               // Clear the error for Response.End
               _error = null;
           }
 
           // ---- the exception. Async completion required (DDB 140655)
           Thread.ResetAbort(); 
        } 
        catch (Exception e) {
            _error = e; 
        }


        // Complete the current async task 
        _completed = true;
        _taskManager.TaskCompleted(_completedSynchronously /*onCallerThread*/); // notify TaskManager 
 
        // Wait for pending AsyncTasks (DDB 140655)
        if (responseEnded) { 
            _taskManager.CompleteAllTasksNow(false /*syncCaller*/);
        }
    }
} 

} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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PageAsyncTask.cs source code in C# .NET

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