.NET-Community-Toolkit/CommunityToolkit.Common/Deferred/EventDeferral.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.ComponentModel;
using System.Threading;
using System.Threading.Tasks;

#pragma warning disable CA1063

namespace CommunityToolkit.Common.Deferred;

/// <summary>
/// Deferral handle provided by a <see cref="DeferredEventArgs"/>.
/// </summary>
public class EventDeferral : IDisposable
{
    //// TODO: If/when .NET 5 is base, we can upgrade to non-generic version
    private readonly TaskCompletionSource<object?> _taskCompletionSource = new();

    internal EventDeferral()
    {
    }

    /// <summary>
    /// Call when finished with the Deferral.
    /// </summary>
    public void Complete() => _taskCompletionSource.TrySetResult(null);

    /// <summary>
    /// Waits for the <see cref="EventDeferral"/> to be completed by the event handler.
    /// </summary>
    /// <param name="cancellationToken"><see cref="CancellationToken"/>.</param>
    /// <returns><see cref="Task"/>.</returns>
#if !NETSTANDARD1_4
    [Browsable(false)]
#endif
    [EditorBrowsable(EditorBrowsableState.Never)]
    [Obsolete("This is an internal only method to be used by EventHandler extension classes, public callers should call GetDeferral() instead on the DeferredEventArgs.")]
    public async Task WaitForCompletion(CancellationToken cancellationToken)
    {
        using (cancellationToken.Register(() => _taskCompletionSource.TrySetCanceled()))
        {
            _ = await _taskCompletionSource.Task;
        }
    }

    /// <inheritdoc/>
    public void Dispose()
    {
        Complete();
    }
}