using System;

public class Program

{

    public static void Main()

    {

        var value = EnumA.Undefined;

        var castResult = (EnumB)Enum.Parse(typeof(EnumB), value.ToString());

        Console.WriteLine(castResult);

    }

    public enum EnumA

    {

        Undefined,

        A,

        B,

        C

    }

    public enum EnumB

    {

        A,

        B,

        C

    }

}