SerializableDictionary

[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]);
     }
 }