private void FetchHistory(PaymentAddress address, UInt64 limit, UInt64 fromHeight, Action <ErrorCode, HistoryCompactList> handler) { GCHandle handlerHandle = GCHandle.Alloc(handler); IntPtr handlerPtr = (IntPtr)handlerHandle; ChainNative.chain_fetch_history(nativeInstance_, handlerPtr, address.NativeInstance, limit, fromHeight, internalFetchHistoryHandler_); }