using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows;

namespace WpfApp55.ViewModel

{

    public class VM : INotifyPropertyChanged

    {

        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propName)

        {

            var handler = PropertyChanged;

            if (handler != null)

            {

                handler(this, new PropertyChangedEventArgs(propName));

            }

        }

        private DelegateCommand UCCmdValue;

        public DelegateCommand UCCmd

        {

            get

            {

                if(UCCmdValue==null)

                {

                    UCCmdValue = new DelegateCommand(UCCmdExecuted, UCCmdCanExecute);

                }

                return UCCmdValue;

            }

        }

        private bool UCCmdCanExecute(object obj)

        {

            return true;

        }

        private void UCCmdExecuted(object obj)

        {

            MessageBox.Show("You had clicked the customized button!");

        }

    }

}

  public class DelegateCommand : ICommand

     {

         private readonly Predicate<object> _canExecute;

         private readonly Action<object> _execute;

         public event EventHandler CanExecuteChanged;

         public DelegateCommand(Action<object> execute)

                        : this(execute, null)

         {

         }

         public DelegateCommand(Action<object> execute,

                        Predicate<object> canExecute)

         {

             _execute = execute;

             _canExecute = canExecute;

         }

         public  bool CanExecute(object parameter)

         {

             if (_canExecute == null)

             {

                 return true;

             }

             return _canExecute(parameter);

         }

         public  void Execute(object parameter)

         {

             _execute(parameter);

         }

         public void RaiseCanExecuteChanged()

         {

             if (CanExecuteChanged != null)

             {

                 CanExecuteChanged(this, EventArgs.Empty);

             }

         }

     }