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Asynchronously wait for Task to complete with timeout

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16 2019
天命终不由人
天命终不由人 2020-11-21 17:49

I want to wait for a Task to complete with some special rules: If it hasn\'t completed after X milliseconds, I want to display a message to the user. And

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  • 长发绾君心
    长发绾君心 (楼主)
    2020-11-21 18:45

    I felt the Task.Delay() task and CancellationTokenSource in the other answers a bit much for my use case in a tight-ish networking loop.

    And although Joe Hoag's Crafting a Task.TimeoutAfter Method on MSDN blogs was inspiring, I was a little weary of using TimeoutException for flow control for the same reason as above, because timeouts are expected more frequently than not.

    So I went with this, which also handles the optimizations mentioned in the blog:

    public static async Task BeforeTimeout(this Task task, int millisecondsTimeout)
{
    if (task.IsCompleted) return true;
    if (millisecondsTimeout == 0) return false;

    if (millisecondsTimeout == Timeout.Infinite)
    {
        await Task.WhenAll(task);
        return true;
    }

    var tcs = new TaskCompletionSource();

    using (var timer = new Timer(state => ((TaskCompletionSource)state).TrySetCanceled(), tcs,
        millisecondsTimeout, Timeout.Infinite))
    {
        return await Task.WhenAny(task, tcs.Task) == task;
    }
}



    An example use case is as such:
    


    var receivingTask = conn.ReceiveAsync(ct);

while (!await receivingTask.BeforeTimeout(keepAliveMilliseconds))
{
    // Send keep-alive
}

// Read and do something with data
var data = await receivingTask;

    
    
    
             
    
                                                        
    
            
            
    
              
                
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