In

public static bool In<T>(this T s, params T[] values)
{
    return values.Any(x => x.Equals(s));
}

public enum VehicleType
{
    Car,
    Bike,
    Truck,
    Bus
}

public bool IsCarOrBike(VehicleType vehicle)
{
    return vehicle.In(VehicleType.Car, VehicleType.Bike);
}

public bool IsValidGender(string textToValidate)
{
    return textToValidate.In("m", "f", "male", "female");
}