unityのinspector内で配列をプルダウンで選択できるようにしたいです。

using System;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;
#if UNITY_EDITOR
using UnityEditor;
#endif
public class ButtonManager : MonoBehaviour
{
    public Button[] Buttons;

    [HideInInspector]
    public int SelectButton;

    private Button UseButton
    {
        get
        {
            if(this.Buttons == null)
            {
                throw new Exception("ボタンのリストがNull");
            }
            if (this.Buttons.Length <= this.SelectButton)
            {
                throw new IndexOutOfRangeException("Indexが超えている");
            }
            return this.Buttons[this.SelectButton];
        }
    }

#if UNITY_EDITOR
    [CustomEditor(typeof(ButtonManager))]
    public class EditorButtonManager : Editor
    {
        public override void OnInspectorGUI()
        {
            base.OnInspectorGUI();

            ButtonManager manager = (ButtonManager)this.target;
            // 未セットの場合はnullがありえる
            if (manager.Buttons == null)
            {
                return;
            }

            manager.SelectButton = EditorGUILayout.Popup(
                manager.SelectButton, 
                manager.Buttons.Select((x) => x.name.ToString()).ToArray()
                );
        }
    }
#endif
}