public static void BuyCandy(PiggyBank piggyBank)
{
if (piggyBank.Coins < 7)
throw new ArgumentException(
"Not enough money for candy!", "piggyBank");
piggyBank.Coins -= 7;
}
public static void TestMutable()
{
// this works fine
var piggyBank = new PiggyBank(5);
MutableTest.DepositCoins(piggyBank);
MutableTest.BuyCandy(piggyBank);
// but this raises an ArgumentException
piggyBank = new PiggyBank(5);
MutableTest.BuyCandy(piggyBank);
MutableTest.DepositCoins(piggyBank);
}
public static void DepositCoins(PiggyBank piggyBank)
{
piggyBank.Coins += 10;
}