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_);
}