Cycles through an enum upward or downward and clamps the index.

CycleEnum.cs

private static T CycleEnum<T>(T type, int direction) where T : Enum
{
    var values = (T[])Enum.GetValues(typeof(T));

    var index = Array.IndexOf(values, type);
    var newIndex = Math.Clamp(index + direction, 0, values.Length - 1);

    return values[newIndex];
}

Example.cs

private enum TestEnum
{
    Foo = 1,
    Bar = 3,
    Baz = 5,
    Qux = 7
}

private TestEnum Test {get; set;}

private void CycleTestUp() => Test = CycleEnum(Test, -1);
private void CycleTestDown() => Test = CycleEnum(Test, +1);