using System;
 
class OnlyOneOption
{
    // Constructor is private so users cannot create their own instances.
    private OnlyOneOption() {}
 
	private static int LastID = 0;
    private readonly int id = ++OnlyOneOption.LastID;
	static public implicit operator int(OnlyOneOption option) { return option.id; }
 
    public static OnlyOneOption OptionA = new OnlyOneOption();
    public static OnlyOneOption OptionB = new OnlyOneOption();
    public static OnlyOneOption OptionC = new OnlyOneOption();
}
 
public class Test
{
	public static void Main()
	{
		OnlyOneOption option = OnlyOneOption.OptionA;
		switch(option) { 
		  case OnlyOneOption.OptionA: break;
		  case OnlyOneOption.OptionB: break;
		  default: throw new InvalidOperationException();
		}
	}
}

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