using System;

using System.ComponentModel;

​

public enum MyGender

{

    Male = 0,

    Female = 1,

}

​

public enum TheirGender

{

    Male = 0,

    Female = 1,

    Unknown = 2,

}

​

public class Program

{   

    public static void Main()

    {

        Console.WriteLine(GetMyGender(TheirGender.Male));

        Console.WriteLine(GetMyGender(TheirGender.Female));

        Console.WriteLine(GetMyGender(TheirGender.Unknown));

        static MyGender GetMyGender(TheirGender theirGender)

            => theirGender switch

            {

                TheirGender.Male => MyGender.Male,

                TheirGender.Female => MyGender.Female,

                _ => throw new InvalidEnumArgumentException(nameof(theirGender), (int)theirGender, typeof(TheirGender))

            };

    }   

}