RelayCommand

RelayCommand.cs

using System;
using System.Windows.Input;

namespace Snippet
{
    public class RelayCommand : ICommand
    {
        readonly Action<object> m_Execute;
        readonly Func<object, bool> m_CanExecute; 

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


        public RelayCommand(Action execute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            m_Execute = _ => execute();
            m_CanExecute = null;
        }

        public RelayCommand(Action<object> execute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            m_Execute = execute;
            m_CanExecute = null;
        }

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

            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));

            m_Execute = _ => execute();
            m_CanExecute = _ => canExecute();
        }

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

            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));

            m_Execute = execute;
            m_CanExecute = canExecute;
        }


        public bool CanExecute(object parameter) => m_CanExecute?.Invoke(parameter) ?? true;

        public void Execute(object parameter) => m_Execute(parameter);


        public static Lazy<RelayCommand> Lazy(Action execute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            return new Lazy<RelayCommand>(() => new RelayCommand(execute));
        }

        public static Lazy<RelayCommand> Lazy(Action<object> execute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            return new Lazy<RelayCommand>(() => new RelayCommand(execute));
        }

        public static Lazy<RelayCommand> Lazy(Action execute, Func<bool> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));

            return new Lazy<RelayCommand>(() => new RelayCommand(execute, canExecute));
        }

        public static Lazy<RelayCommand> Lazy(Action<object> execute, Func<object, bool> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException(nameof(execute));

            if (canExecute == null)
                throw new ArgumentNullException(nameof(canExecute));

            return new Lazy<RelayCommand>(() => new RelayCommand(execute, canExecute));
        }

    }
}