AsyncCommand

using System;
using System.Threading.Tasks;
using System.Windows.Input;

class AsyncCommand : ICommand {
	public Boolean CanExecute(Object parameter = null) => !IsRunning;

	public event EventHandler CanExecuteChanged = delegate { };

	public async void Execute(Object parameter = null) {
		IsRunning = true;
		try {
			await asyncAction();
		}
		finally {
			IsRunning = false;
		}
	}

	private readonly Func<Task> asyncAction;

	public AsyncCommand(Func<Task> asyncAction) {
		this.asyncAction = asyncAction;
	}

	private Boolean isRunning;
	private Boolean IsRunning {
		get {
			return isRunning;
		}
		set {
			isRunning = value;
			CanExecuteChanged.Invoke(this, EventArgs.Empty);
		}
	}
}