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//------------------------------------------------------------------------------
// <copyright file="PageAsyncTaskManager.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.UI {
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
// Handles execution of asynchronous tasks that are registered with a Page
internal sealed class PageAsyncTaskManager {
private bool _executeTasksAsyncHasCompleted = false;
private readonly Queue<IPageAsyncTask> _registeredTasks = new Queue<IPageAsyncTask>();
public void EnqueueTask(IPageAsyncTask task) {
if (_executeTasksAsyncHasCompleted) {
// don't allow multiple calls to the execution routine
throw new InvalidOperationException(SR.GetString(SR.PageAsyncManager_CannotEnqueue));
}
_registeredTasks.Enqueue(task);
}
public async Task ExecuteTasksAsync(object sender, EventArgs e, CancellationToken cancellationToken, AspNetSynchronizationContextBase syncContext, IRequestCompletedNotifier requestCompletedNotifier) {
try {
while (_registeredTasks.Count > 0) {
// if canceled, propagate exception to caller and stop executing tasks
cancellationToken.ThrowIfCancellationRequested();
// if request finished, stop executing tasks
if (requestCompletedNotifier.IsRequestCompleted) {
return;
}
// execute this task
IPageAsyncTask task = _registeredTasks.Dequeue();
using (syncContext.AllowVoidAsyncOperationsBlock()) {
await task.ExecuteAsync(sender, e, cancellationToken);
}
}
}
finally {
_executeTasksAsyncHasCompleted = true;
}
}
}
}
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