namespace UpdateObjectInstance;

internal class Program
{
    public static void Main(string[] args)
    {
        S s = new S();
        s.X = 10;
        Update(s);
        Console.WriteLine(s.X);
    }

    public static void Update(S s)
    {
        s.X = 20;
    }
}

record class S
{
    public int X;
}