Why is collision.contacts causing a compiler error

I am new to Unity Programming so the compiler error has me stumped. Any help is appreciated.

My Code is meant to make a ball reflect, but it is giving me a compiler error on line 11 at collision.contacts.
Could anyone tell me what is wrong, because this is what the scripting reference did. I have also tried this with various types of capitalization.

The Compiler’s Error is: " ‘Collision’ does not contain a definition for ‘contacts’ accepting a first argument of the type ‘Collision’ could be found"

The code is:

using UnityEngine;
using System.Collections;

public class Collision : MonoBehaviour {

public Vector3 move;

void Update () {
 void OnCollisionEnter (Collision collision) {
 ContactPoint contact = collision.contacts[0];
 Vector3.Reflect( move, contact.normal);
     print("Collision is working!");

Ha, subtle

Your script is defining a new class called Collision in the global namespace so it is hiding UnityEngine.Collision - change the name of your Collision class to say MyCollision and it will all work fine.