DelegateCommand.cs

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

namespace ICSheet5e.Views
{
    class DelegateCommand<T> : ICommand
    {
        private readonly Predicate<T> _canExecute;
        private readonly Action<T> _execute;

        public DelegateCommand(Action<T> execute) : this(execute, null)
        {
        }

        public DelegateCommand(Action<T> execute, Predicate<T> canExecute)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

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

            return _canExecute((parameter == null) ? default(T) : (T)Convert.ChangeType(parameter, typeof(T)));
        }

        public void Execute(object parameter)
        {
            _execute((parameter == null) ? default(T) : (T)Convert.ChangeType(parameter, typeof(T)));
        }

        public event EventHandler CanExecuteChanged;
        public void RaiseCanExecuteChanged()
        {
            CommandManager.InvalidateRequerySuggested();
            CanExecuteChanged?.Invoke(this, EventArgs.Empty);
        }
    }
}