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//------------------------------------------------------------------------------
// <copyright file="PageAsyncTaskApm.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.UI {
using System;
using System.Threading;
using System.Threading.Tasks;
// Represents an IPageAsyncTask that follows APM (Begin / End)
internal sealed class PageAsyncTaskApm : IPageAsyncTask {
private readonly BeginEventHandler _beginHandler;
private readonly EndEventHandler _endHandler;
private readonly object _state;
public PageAsyncTaskApm(BeginEventHandler beginHandler, EndEventHandler endHandler, object state) {
_beginHandler = beginHandler;
_endHandler = endHandler;
_state = state;
}
public async Task ExecuteAsync(object sender, EventArgs e, CancellationToken cancellationToken) {
// The CancellationToken is ignored in APM since every call to Begin must be matched by
// a call to End, otherwise memory leaks and other badness can occur.
// The reason we don't use TaskFactory.FromAsync is that we need the end handler to execute
// within the current synchronization context, but FromAsync doesn't make that guarantee.
// The callback that marks the TaskCompletionSource as complete can execute synchronously or asynchronously.
TaskCompletionSource<object> taskCompletionSource = new TaskCompletionSource<object>();
IAsyncResult asyncResult = _beginHandler(sender, e, _ => { taskCompletionSource.SetResult(null); }, _state);
await taskCompletionSource.Task;
_endHandler(asyncResult);
}
}
}
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