private void FetchBlockHeaderByHash(byte[] blockHash, Action <ErrorCode, Header, UInt64> handler) { var managedHash = new hash_t { hash = blockHash }; IntPtr contextPtr = CreateContext(handler, managedHash); ChainNative.chain_fetch_block_header_by_hash(nativeInstance_, contextPtr, managedHash, internalFetchBlockHeaderHandlerByHash_); }