How to add a Timeout to Console.ReadLine()?

Question

I have a console app in which I want to give the user x seconds to respond to the prompt. If no input is made after a certain period of time, program logic should

Answer 1

Here is a solution that uses Console.KeyAvailable. These are blocking calls, but it should be fairly trivial to call them asynchronously via the TPL if desired. I used the standard cancellation mechanisms to make it easy to wire in with the Task Asynchronous Pattern and all that good stuff.

public static class ConsoleEx
{
  public static string ReadLine(TimeSpan timeout)
  {
    var cts = new CancellationTokenSource();
    return ReadLine(timeout, cts.Token);
  }

  public static string ReadLine(TimeSpan timeout, CancellationToken cancellation)
  {
    string line = "";
    DateTime latest = DateTime.UtcNow.Add(timeout);
    do
    {
        cancellation.ThrowIfCancellationRequested();
        if (Console.KeyAvailable)
        {
            ConsoleKeyInfo cki = Console.ReadKey();
            if (cki.Key == ConsoleKey.Enter)
            {
                return line;
            }
            else
            {
                line += cki.KeyChar;
            }
        }
        Thread.Sleep(1);
    }
    while (DateTime.UtcNow < latest);
    return null;
  }
}

There are some disadvantages with this.

• You do not get the standard navigation features that ReadLine provides (up/down arrow scrolling, etc.).
• This injects '\0' characters into input if a special key is press (F1, PrtScn, etc.). You could easily filter them out by modifying the code though.