Serializable string to generic map in Unity

SerializableMap.cs

using System;
using System.Collections.Generic;
using UnityEngine;

namespace Lumic.Utils
{
    /// <summary>
    /// Assumes string keys.
    /// Kind of works, use the +/- buttons on the "Keys". +/- Buttons on values list does't work.
    /// Example usage:
    ///     [Serializable] public class MaterialMap : SerializableMap<Material> { } // create concrete class first
    ///     ...
    ///     public MaterialMap map = new MaterialMap(); // in MonoBehaviour
    /// </summary>
    [Serializable]
    public class SerializableMap<TValue> : Dictionary<string, TValue>, ISerializationCallbackReceiver
    {
        private static int AutoKeyCount = 0;

        [SerializeField] private List<string> keys = new List<string>();
        [SerializeField] private List<TValue> values = new List<TValue>();

        public void OnBeforeSerialize ()
        {
            this.keys.Clear();
            this.values.Clear();
            foreach (var pair in this)
            {
                this.keys.Add(pair.Key);
                this.values.Add(pair.Value);
            }
        }

        public void OnAfterDeserialize ()
        {
            this.Clear();

            var count = keys.Count;

            for (var i = 0; i < count; i++)
            {
                string k;
                if (i == this.keys.Count - 1 && this.keys.Count > this.values.Count)
                {
                    k = GetAutoKey();
                } else
                {
                    k = this.keys[i];
                }

                var v = (i > this.values.Count - 1) ? default(TValue) : this.values[i];
                this.Add(k, v);
            }
        }

        private static string GetAutoKey ()
        {
            return $"Element{AutoKeyCount++}";
        }
    }
}