oap_labs/ConsoleApp2/Program.cs

using System;

class Client
{
    public string Name { get; set; }
    public int Age { get; set; }

    public Client(string name, int age)
    {
        Name = name;
        Age = age;
    }
}

class Program
{
    static void Main()
    {
        List<Client> users = new List<Client>
        {
            new Client("Маша", 18),
            new Client("Алиса", 23),
            new Client("Саша", 30),
            new Client("Вова", 25),
            new Client("Алена", 37)
        };

        var result = users
            .OrderBy(u => u.Name)
            .ThenBy(u => u.Age);

        foreach (Client u in result)
            Console.WriteLine($"{u.Name} - {u.Age}");
    }
}