public void SetAt(ExpressionKey key, DLG_CONVERT to, DLG_CONVERT back)
        {
            ConvertPair pair;

            if (Impl.TryGetValue(key, out pair))
            {
                pair.To = to; pair.Back = back;
            }
            else
            {
                Impl[key] = new ConvertPair(to, back);
            }
        }
 public bool TryGetValue(ExpressionKey key, out ConvertPair value)
 {
     return(Impl.TryGetValue(key, out value));
 }
 public void Add(ExpressionKey key, ConvertPair value)
 {
     Impl.Add(key, value);
 }