using System;

using System.Linq;

using System.Reflection;

using System.ComponentModel.DataAnnotations;

public class Program

{

    public static void Main()

    {

        var names = Enum.GetNames(typeof(Countries)).ToList();

        foreach( var name in names )

            Console.WriteLine(name);

        Console.WriteLine();

        names = Enum.GetValues<Countries>().Select(v => v.GetDisplayName()).ToList();

        foreach( var name in names )

            Console.WriteLine(name);

    }

}

​

public enum Countries

{

    Australia,

    [Display(Name="New Zealand")] 

    NewZealand,

}

​

public static class CountriesExtensions

{

    public static string GetDisplayName(this Countries enumValue)

    {

        return enumValue.GetType()

                        .GetMember(enumValue.ToString())

                        .First()

                        .GetCustomAttribute<DisplayAttribute>()

                        ?.GetName() ?? enumValue.ToString();

    }

}