Mono.Cecil - simple example how to get method body

I have been searching for a newbie question, but can't find a simple example. Can anyone give me a simple example how to get MethodBody into most available string result? like:

using Mono.Cecil;
using Mono.Cecil.Cil;

namespace my
{
    public class Main
    {


        public Main()
        {
             // phseudo code, but doesnt work
            Console.Write    getMethod("HelloWorld").GetMethodBody().ToString()   );
        }



        public void HelloWorld(){
             MessageBox.Show("Hiiiiiiiiii");
        }



    }

}