ActionCommand.cs

// ReSharper disable UnusedMemberInSuper.Global

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

namespace Sudoku
{
    public interface IAsyncCommand<in T> : ICommand
    {
        Task ExecuteAsync(T parameter);
        bool CanExecute(T parameter);
    }

    public class AsyncCommand<T> : IAsyncCommand<T>
    {
        private bool _isExecuting;
        private readonly Func<T, Task> _execute;
        private readonly Func<T, bool> _canExecute;

        public AsyncCommand(Func<T, Task> execute, Func<T, bool> canExecute = null)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

        public event EventHandler CanExecuteChanged
        {
            add => CommandManager.RequerySuggested += value;
            remove => CommandManager.RequerySuggested -= value;
        }

        public bool CanExecute(T parameter)
        {
            return !_isExecuting && (_canExecute?.Invoke(parameter) ?? true);
        }

        public async Task ExecuteAsync(T parameter)
        {
            if (CanExecute(parameter))
            {
                try
                {
                    _isExecuting = true;
                    await _execute(parameter);
                }
                finally
                {
                    _isExecuting = false;
                }
            }
        }

        #region Explicit implementations

        bool ICommand.CanExecute(object parameter)
        {
            return CanExecute((T)parameter);
        }

        void ICommand.Execute(object parameter)
        {
            //Fire and forget
#pragma warning disable 4014
            ExecuteAsync((T)parameter);
#pragma warning restore 4014
        }

        #endregion
    }
}