WpfViewModelFirst/WpfViewModelFirst/CustomCommand.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace WpfViewModelFirst
{
    public class CustomCommand : ICommand 
    {
        private readonly Action<object?> _execute;
        private readonly Predicate<object?>? _canExecute;

        public CustomCommand(Action<object?> execute, Predicate<object?> canExecute)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

        public CustomCommand(Action<object?> execute)
        {
            _execute = execute;
        }

        public bool CanExecute(object? parameter)
        {
            return _canExecute == null || _canExecute(parameter);
        }

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

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

    }
}