public ReactiveDictionaryChange(TKey key, TValue value, ReactiveDictionaryChangeReason reason)
 {
     this.ChangeReason = reason;
     this.Key          = key;
     this.Value        = value;
 }
 public ReactiveDictionaryChange(KeyValuePair <TKey, TValue> pair, ReactiveDictionaryChangeReason reason)
 {
     this.ChangeReason = reason;
     this.Key          = pair.Key;
     this.Value        = pair.Value;
 }