interface IAutomobile
{
  string LicensePlate { get; }
  double Speed { get; }
  int Wheels { get; }
}

// The IAutomobile interface has three properties. Any class that implements this interface must have these three properties.

public interface IAccount
{
  void PayInFunds ( decimal amount );
  bool WithdrawFunds ( decimal amount );
  decimal GetBalance ();
}

// The IAccount interface has three methods to implement.

public class CustomerAccount : IAccount
{ }

// This CustomerAccount class is labeled with : IAccount, which means that it will implement that interface.