public ImmutableDictionary<UInt256, UnconfirmedTx> GetTransactionsSpending(TxOutputKey prevTxOutputKey) { ImmutableDictionary<UInt256, UnconfirmedTx>.Builder unconfirmedTxes; if (unconfirmedTxesByPrevTxOutputKey.Value.TryGetValue(prevTxOutputKey, out unconfirmedTxes)) return unconfirmedTxes.ToImmutable(); else return ImmutableDictionary<UInt256, UnconfirmedTx>.Empty; }