private void FetchBlockHeaderByHashTxSizes(byte[] blockHash, FetchBlockHeaderByHashTxsSizeHandler handler) { var managedHash = new hash_t { hash = blockHash }; IntPtr contextPtr = CreateContext(handler, managedHash); ChainNative.chain_fetch_block_header_by_hash_txs_size(nativeInstance_, contextPtr, managedHash, internalFetchBlockHeaderByHashTxsSizeHandler_); }