using System;

using System.Linq;

using System.Reflection;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(

            typeof(TestEnum).GetTypeInfo().DeclaredFields.First(x => x.Name.Equals("value__")).FieldType.ToString()

        );

        Console.WriteLine(

            typeof(TestEnum).GetTypeInfo().DeclaredFields.First(x => x.FieldHandle.GetType().Equals(typeof(RuntimeFieldHandle))).FieldType.ToString()

        );

​

        Console.WriteLine(

            ((FieldInfo)typeof(TestEnum).GetTypeInfo().DeclaredMembers.First(x => x.Name.Equals("value__"))).FieldType.ToString()

        );

        Console.WriteLine(

            ((FieldInfo)typeof(TestEnum).GetTypeInfo().DeclaredMembers.First(x => ((FieldInfo)x).FieldHandle.GetType().Equals(typeof(RuntimeFieldHandle)))).FieldType.ToString()

        );

    }

}

​

public enum TestEnum : long

{

    AAA,

    BBB,

    CCC

}