WPF Prism v4 MVVM

1.Install-package Prism -v 4

2.

using Microsoft.Practices.Prism;
using Microsoft.Practices.Prism.Commands;
using Microsoft.Practices.Prism.Events;
using Microsoft.Practices.Prism.Interactivity;
using Microsoft.Practices.Prism.Modularity;
using Microsoft.Practices.Prism.Logging;
using Microsoft.Practices.Prism.Regions;
using Microsoft.Practices.Prism.ViewModel;

3.

private DelegateCommand<object> clickCmd;
        public DelegateCommand<object> ClickCmd
        {
            get
            {
                if(clickCmd==null)
                {
                    clickCmd = new DelegateCommand<object>(ClickCmdExecuted);
                }
                return clickCmd;
            }
        }

        private void ClickCmdExecuted(object obj)
        {
            System.Windows.MessageBox.Show(obj.ToString());
        }