BitcoinSecret nicoSecret = new BitcoinSecret("cPY2XauRnLnruVQyEfgzB7Wpoxhsc94e4S3DDYecz3dMcoEDEKYm");
BitcoinSecret yourSecret = new BitcoinSecret("xxxxx");
Money toSend = Money.Coins(0.01m);
Money miningFee = Money.Coins(0.001m);


List<Coin> coinsToSpend = new List<Coin>();
Money current = Money.Zero;

QBitNinjaClient client = new QBitNinjaClient(Network.TestNet);
var balance = client.GetBalance(nicoSecret.GetAddress(), true).Result;
foreach(var entry in balance.Operations)
{
    foreach(var coin in entry.ReceivedCoins)
    {
        if(current < miningFee + toSend)
        {
            coinsToSpend.Add((Coin)coin);
            current += (Money)coin.Amount;
        }
    }
}

Transaction tx = new Transaction();
foreach(var coin in coinsToSpend)
{
    tx.AddInput(new TxIn(coin.Outpoint));
}

tx.AddOutput(new TxOut(toSend, yourSecret.GetAddress()));
tx.AddOutput(new TxOut(current - miningFee - toSend, nicoSecret.GetAddress()));

tx.Sign(nicoSecret, coinsToSpend.ToArray());
client.Broadcast(tx).Wait();

System.Console.WriteLine(tx);