IterationMethodsForEnum.cs

namespace ExtensionMethods
{
    public static class MyExtensions
    {
        public static void Next(this ref MyEnum item)
        {
            int count = Enum.GetNames(typeof(MyEnum)).Length;
            int index = item.GetHashCode();
            int nextIndex = index + 1;
            if (nextIndex >= count) nextIndex = 0;
            item = (MyEnum) nextIndex;
        }
        
        public static void Previous(this ref MyEnum item)
        {
            int count = Enum.GetNames(typeof(MyEnum)).Length;
            int index = item.GetHashCode();
            int prevIndex = index - 1;
            if (prevIndex <= 0) prevIndex = count - 1;
            item = (MyEnum) prevIndex;
        }
    }
}