WowUp/WowUp.WPF/Utilities/Command.cs

using System;
using System.Windows.Input;

namespace WowUp.WPF.Utilities
{
    public class Command : ICommand
    {
        readonly Func<object, bool> _canExecute;
        readonly Action<object> _execute;
        readonly WeakEventManager _weakEventManager = new WeakEventManager();
        public Command(Action<object> execute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            _execute = execute;
        }

        public Command(Action execute) : this(o => execute())
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));
        }

        public Command(Action<object> execute, Func<object, bool> canExecute) : this(execute)
        {
            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));

            _canExecute = canExecute;
        }

        public Command(Action execute, Func<bool> canExecute) : this(o => execute(), o => canExecute())
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));
            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));
        }

        public bool CanExecute(object parameter)
        {
            if (_canExecute != null)
                return _canExecute(parameter);

            return true;
        }

        public event EventHandler CanExecuteChanged
        {
            add { _weakEventManager.AddEventHandler(value); }
            remove { _weakEventManager.RemoveEventHandler(value); }
        }

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

        public void ChangeCanExecute()
        {
            _weakEventManager.HandleEvent(this, EventArgs.Empty, nameof(CanExecuteChanged));
        }
    }
}