MossyUpdater/ViewModels/RelayCommand.cs

using System.Windows.Input;

namespace MossyUpdater.ViewModels
{
    public class RelayCommand : ICommand
    {
        private readonly Action<object?> _execute;
        private readonly Predicate<object?>? _canExecute;

        public RelayCommand(Action<object?> execute, Predicate<object?>? canExecute = null)
        {
            _execute = execute ?? throw new ArgumentNullException(nameof(execute));
            _canExecute = canExecute;
        }

        public RelayCommand(Action execute, Func<bool>? canExecute = null)
            : this(_ => execute(), canExecute == null ? null : _ => canExecute())
        {
        }

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

        public bool CanExecute(object? parameter)
        {
            return _canExecute?.Invoke(parameter) ?? true;
        }

        public void Execute(object? parameter)
        {
            _execute(parameter);
        }

        public void RaiseCanExecuteChanged()
        {
            CommandManager.InvalidateRequerySuggested();
        }
    }

    public class AsyncRelayCommand : ICommand
    {
        private readonly Func<object?, Task> _execute;
        private readonly Predicate<object?>? _canExecute;
        private bool _isExecuting;

        public AsyncRelayCommand(Func<object?, Task> execute, Predicate<object?>? canExecute = null)
        {
            _execute = execute ?? throw new ArgumentNullException(nameof(execute));
            _canExecute = canExecute;
        }

        public AsyncRelayCommand(Func<Task> execute, Func<bool>? canExecute = null)
            : this(_ => execute(), canExecute == null ? null : _ => canExecute())
        {
        }

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

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

        public async void Execute(object? parameter)
        {
            if (!CanExecute(parameter))
                return;

            try
            {
                _isExecuting = true;
                RaiseCanExecuteChanged();
                await _execute(parameter);
            }
            finally
            {
                _isExecuting = false;
                RaiseCanExecuteChanged();
            }
        }

        public void RaiseCanExecuteChanged()
        {
            CommandManager.InvalidateRequerySuggested();
        }
    }
}