Waiting for a keypress asynchronously in a C# console app

This one’s kind of specific, but sometimes when you’re writing a console app that does a lot of asynchronous stuff, and you want to cancel it at any time by pressing escape. 

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However, Console.ReadKey is blocking… so that’s not super great.

CancellationToken

First, make use of the cancellation tokens.  I’ve talked about them before, but they allow you to cancel in-flight asynchronous operations.  Essentially, we will want to create our own asynchronous task that waits for a key press and then cancels the cancellation token, thereby stopping whatever kind of asynchronous processes you have running.

	public void MonitorKeypress(CancellationToken cancellationToken)
	{
	ConsoleKeyInfo cki = new ConsoleKeyInfo();
	do
	{
	// true hides the pressed character from the console
	cki = Console.ReadKey(true);
	// Wait for an ESC
	} while (cki.Key != ConsoleKey.Escape);
	// Cancel the token
	cancellationToken.Cancel();
	}

view raw MonitorKeypressAsync.cs hosted with by GitHub

Task.Run

Then you just need to launch this method inside of a Task so it can run asynchronously.

	// Launch the task to wait for a keypress
	Task consoleKeyTask = Task.Run(() => { MonitorKeypress(); });
	// ... Launch other async tasks ...
	// Waits for the keypress to end it all
	await consoleKeyTask;

view raw Main.cs hosted with by GitHub

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