Unity_Utils/SerializableDictionary.cs

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

[Serializable]
public class SerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue>, ISerializationCallbackReceiver
{
    [SerializeField] private List<TKey> _keys = new List<TKey>();
    [SerializeField] private List<TValue> _values = new List<TValue>();
    
    public void OnBeforeSerialize()
    {
        _keys.Clear();
        _values.Clear();

        foreach (KeyValuePair<TKey,TValue> pair in this)
        {
            _keys.Add(pair.Key);
            _values.Add(pair.Value);
        }
    }

    public void OnAfterDeserialize()
    {
        Clear();

        if (_keys.Count != _values.Count)
        {
            throw new Exception(
                $"There are {_keys.Count} keys and {_values.Count} values after deserialization." +
                " Make sure that both key and value types are serializable.");
        }

        for (int i = 0; i < _keys.Count; ++i)
        {
            Add(_keys[i], _values[i]);
        }
    }
}