using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var allValues = Enum.GetValues(typeof (MyEnum)).Cast<MyEnum>().Except(new[]{MyEnum.D}).ToArray();

        foreach (var val in allValues)

        {

            Console.WriteLine(val);

        }

    }

}

​

public enum MyEnum

{

    A,

    B,

    C,

    D

}