What is wrong with my Counter Script? (C#)

Hi Guys,

I dont know what is wrong with my counter script. i know how to do it in javascript but every other script in my game is c# and i want them all to connect.

Thank You,

 using UnityEngine;
 using System.Collections;
 
 public class Counter : MonoBehaviour {
 
     // Use this for initialization
     int Counter = 0;
     
     void  Update (){
         
         Counter++;
         guiText.text = ""+Counter;
         
         
     }
 }