return new RelayCommand(p => MessageBox.Show("It worked."));

public RelayCommand(Action<object> execute, Predicate<object> canExecute)
{
    if (execute == null)
        throw new ArgumentNullException("execute");

    _execute = execute;
    _canExecute = canExecute;
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TestLambda24
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] numbers = { 6, 3, 7, 4, 8 };

            //Console.WriteLine("The addition result is {0}.", Tools.ProcessNumbers(p => Tools.AddNumbers, numbers));
            Console.WriteLine("The addition result is {0}.", Tools.ProcessNumbers(Tools.AddNumbers, numbers));

            //Console.WriteLine("The multiplication result is {0}.", Tools.ProcessNumbers(p => Tools.MultiplyNumbers, numbers));
            Console.WriteLine("The multiplication result is {0}.", Tools.ProcessNumbers(Tools.MultiplyNumbers, numbers));

            Console.ReadLine();
        }
    }

    class Tools
    {
        public static int ProcessNumbers(Func<int[], int> theMethod, int[] integers)
        {
            return theMethod(integers);
        }

        public static int AddNumbers(int[] numbers)
        {
            int result = 0;
            foreach (int i in numbers)
            {
                result += i;
            }
            return result;
        }

        public static int MultiplyNumbers(int[] numbers)
        {
            int result = 1;
            foreach (int i in numbers)
            {
                result *= i;
            }
            return result;
        }
    }

}

static void Main(string[] args)
{
    int[] numbers = { 6, 3, 7, 4, 8 };

    Console.WriteLine("The addition result is {0}.",
        Tools.ProcessNumbers(p => Tools.AddNumbers(p), numbers));

    Console.WriteLine("The multiplication result is {0}.",
        Tools.ProcessNumbers(p => Tools.MultiplyNumbers(p), numbers));

    Console.ReadLine();
}