Add Signature

public class AddSignatureExample : IExample
{
    private static readonly IRpcClient rpcClient = ClientFactory.GetClient(Cluster.TestNet);

    private const string MnemonicWords =
        "route clerk disease box emerge airport loud waste attitude film army tray " +
        "forward deal onion eight catalog surface unit card window walnut wealth medal";

    public void Run()
    {
        Wallet.Wallet wallet = new Wallet.Wallet(MnemonicWords);

        Account fromAccount = wallet.GetAccount(10);
        Account toAccount = wallet.GetAccount(8);

        RequestResult<ResponseValue<BlockHash>> blockHash = rpcClient.GetRecentBlockHash();
        Console.WriteLine($"BlockHash >> {blockHash.Result.Value.Blockhash}");

        TransactionBuilder txBuilder = new TransactionBuilder()
            .SetRecentBlockHash(blockHash.Result.Value.Blockhash)
            .SetFeePayer(fromAccount)
            .AddInstruction(SystemProgram.Transfer(fromAccount.PublicKey, toAccount.PublicKey, 10000000))
            .AddInstruction(MemoProgram.NewMemo(fromAccount.PublicKey, "Hello from Sol.Net :)"));

        byte[] msgBytes = txBuilder.CompileMessage();
        byte[] signature = fromAccount.Sign(msgBytes);

        byte[] tx = txBuilder.AddSignature(signature)
            .Serialize();

        Console.WriteLine($"Tx base64: {Convert.ToBase64String(tx)}");
        RequestResult<ResponseValue<SimulationLogs>> txSim = rpcClient.SimulateTransaction(tx);
        string logs = Examples.PrettyPrintTransactionSimulationLogs(txSim.Result.Value.Logs);
        Console.WriteLine($"Transaction Simulation:\n\tError: {txSim.Result.Value.Error}\n\tLogs: \n" + logs);
        RequestResult<string> firstSig = rpcClient.SendTransaction(tx);
        Console.WriteLine($"First Tx Signature: {firstSig.Result}");
    }
}