Unity GUI Combobox or Dropdown

I'm using C# Script. Create C# Script named Dropdown. This method is when the button clicked, another button show.

using UnityEngine;
using System.Collections;

public class Dropdown : MonoBehaviour {
 
 public string[] items;
 public Rect Box;
 public string slectedItem = "";
 bool editing = false;
 
 void OnGUI(){
  if (GUI.Button(Box, slectedItem)){
   editing = true;
  }
  
  if (editing){
   for (int x = 0; x < items.Length; x++){
    if (GUI.Button(new Rect(Box.x, (Box.height * x) + Box.y + Box.height, Box.width, Box.height), items[x])){
     slectedItem = items[x];
     editing = false;
    }
   }
  }
  
 }
}

Attach the script in game object main camera then setting value.

 Play and see the Result. When click the Number button show other button.

The source of this tutorial https://www.youtube.com/watch?v=WfvjA8mullw