CTransaction tx; // populate transaction fields uint256 txid = tx.GetHash();
const CTransaction& tx = GetTransactionFromMemoryPool(txid); uint256 hash = tx.GetHash();In this example, we retrieve a transaction from the memory pool (where unconfirmed transactions are stored) using its transaction ID, txid. We then use the GetHash method of the retrieved transaction to calculate its hash and store it in a uint256 variable called hash. The CTransaction class and its GetHash method are part of the Bitcoin Core package library.