using System.Collections;

using System.Globalization;

using System.Linq.Expressions;

using System.Reflection;

using System.Text;

using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var test = new Test();

        test.ToMails = new List<string>() { "123123" };

        test.ToMails.ForEach(t => {

                    Console.WriteLine(t);

​

        });

    }

    public class Test {

     public List<string> RegistrationUserEmails { get; set; } = new();

    public List<string> RegistrationOutsidesEmails { get; set; } = new();

    // Mail info

    public List<string> ToMails

    {

        get => this.RegistrationUserEmails.Concat(this.RegistrationOutsidesEmails).Distinct().ToList();

        set

        {

            RegistrationUserEmails = value;

            RegistrationOutsidesEmails = new();

        }

    }

}

}

​

​