var coins = utxos.GetUnspentCoins();
var keys = utxos.GetKeys(userExtKey);
TransactionBuilder builder = Network.Main.CreateTransactionBuilder();
builder.Send(new Key(), Money.Coins(0.5m));
builder.SetChange(changeAddress.ScriptPubKey);
var fallbackFeeRate = new FeeRate(Money.Satoshis(100), 1);
var feeRate = tester.Client.GetFeeRate(1, fallbackFeeRate).FeeRate;
builder.SendEstimatedFees(feeRate);
var tx = builder.BuildTransaction(true);
var result = client.Broadcast(tx);
Console.WriteLine("Success!");
else if(result.RPCCode.HasValue && result.RPCCode.Value == RPCErrorCode.RPC_TRANSACTION_REJECTED)
Console.WriteLine("We probably got a conflict, let's try again!");
Console.WriteLine(quot;Something is really wrong {result.RPCCode} {result.RPCCodeMessage} {result.RPCMessage}");