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//--------------------------------------------------------------------------

// 

//  Copyright (c) Microsoft Corporation.  All rights reserved. 

// 

//  File: TaskFactoryExtensions_FromAsync.cs

//

//--------------------------------------------------------------------------

namespace System.Threading.Tasks

{

    /// <summary>Extensions for TaskFactory.</summary>

    public static partial class TaskFactoryExtensions

    {

        /// <summary>Creates a Task that will be completed when the specified WaitHandle is signaled.</summary>

        /// <param name="factory">The target factory.</param>

        /// <param name="waitHandle">The WaitHandle.</param>

        /// <returns>The created Task.</returns>

        public static Task FromAsync(this TaskFactory factory, WaitHandle waitHandle)

        {

            if (factory == null) throw new ArgumentNullException("factory");

            if (waitHandle == null) throw new ArgumentNullException("waitHandle");

            var tcs = new TaskCompletionSource<object>();

            var rwh = ThreadPool.RegisterWaitForSingleObject(waitHandle, delegate { tcs.TrySetResult(null); }, null, -1, true);

            var t = tcs.Task;

            t.ContinueWith(_ => rwh.Unregister(null), TaskContinuationOptions.ExecuteSynchronously);

            return t;

        }

    }

}