SerializableDictionary.cs

using UnityEngine;
using System.Collections.Generic;

[System.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> ();

	// save the dictionary to lists
	public void OnBeforeSerialize () {
		keys.Clear ();
		values.Clear ();
		foreach (KeyValuePair<TKey, TValue> pair in this) {
			keys.Add (pair.Key);
			values.Add (pair.Value);
		}
	}

	// load dictionary from lists
	public void OnAfterDeserialize () {
		this.Clear ();

		if (keys.Count != values.Count)
			throw new System.Exception (string.Format ("there are {0} keys and {1} values after deserialization. Make sure that both key and value types are serializable."));

		for (int i = 0; i < keys.Count; i++)
			this.Add (keys[i], values[i]);
	}
}