using System;

using System.Linq;

using System.Collections.Generic;

using System.Collections.Immutable;

public class Program

{

    static void Main(string[] args)

    {

        var current = new Test { Foo = "Hello" };

        var originalProperties = GetProps(current);

        var t = (current, originalProperties);

​

        Console.WriteLine(t.originalProperties["Foo"]);

        Console.WriteLine(((List<string>)t.originalProperties["Bar"]).Count());

​

        Console.WriteLine(Environment.NewLine);

​

        t.current.Foo = "Goodbye";

        t.current.Bar.Add("abcd");

​

        Console.WriteLine(t.originalProperties["Foo"]);

        Console.WriteLine(((List<string>)t.originalProperties["Bar"]).Count());

    }

​

    public static ImmutableDictionary<string, object> GetProps(Test t)

        => t.GetType()

            .GetProperties()

            .ToDictionary(x => x.Name, x => x.GetValue(t))

            .ToImmutableDictionary();

​

    public class Test

    {

        public string Foo { get; set; }

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

    }

}