Unity 2D On Trigger Enter is not working, getting error

I am trying to get my game to switch scenes when i collide with a door entrance but i keep getting this error:

Assets/OnTriggerEnder2D.cs(4,14): error CS0101: The namespace global::' already contains a definition for ExampleClass'

With this code:

 using UnityEngine;
 using System.Collections;
 
 public class ExampleClass : MonoBehaviour {
     public bool characterInQuicksand;
     void OntriggerEnter2D(Collider2D other) {
         characterInQuicksand = true;
     }
 }