List<T>去重

    static void Main(string[] args)
    {
        List<int> users = new List<int>()
        {
            1,2,3,4,5,1,2,3,4,5
        };

        var count = users.Count;

        users = new HashSet<int>(users).ToList();

        var count2 = users.Count;
        Console.WriteLine($"去重前：{count} 去重后：{count2}");
    }

去重前：10 去重后：5