Wrap an event as Task

TaskFromEvent.cs

/// <summary>
/// Wrap an event as Task
/// </summary>
/// <see href="https://stackoverflow.com/a/22798789/1768303"/>
public static async Task<TEventArgs> FromEvent<TEventHandler, TEventArgs>(
    Func<Action<TEventArgs>, Action, Action<Exception>, TEventHandler> getHandler,
    Action<TEventHandler> subscribe,
    Action<TEventHandler> unsubscribe,
    Action<Action<TEventArgs>, Action, Action<Exception>> initiate,
    CancellationToken token = default) where TEventHandler : Delegate
{
    var tcs = new TaskCompletionSource<TEventArgs>();

    Action<TEventArgs> complete = args => tcs.TrySetResult(args);
    Action cancel = () => tcs.TrySetCanceled();
    Action<Exception> reject = ex => tcs.TrySetException(ex);

    TEventHandler handler = getHandler(complete, cancel, reject);

    subscribe(handler);
    try
    {
        using (token.Register(() => tcs.TrySetCanceled(), useSynchronizationContext: false))
        {
            initiate(complete, cancel, reject);
            return await tcs.Task;
        }
    }
    finally
    {
        unsubscribe(handler);
    }
}