using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;

var products = new List<Product> {
    new(1, "Car"),
    new(2, "Jet")
};

var dic1 = products.ToDictionary(p => p.Id);
//dic1 is Dictionary<int, Product> 

Console.WriteLine(JsonSerializer.Serialize(dic1));

var dic2 = products.ToDictionary(
    p => p.Id, p => p.Name);
//dic2 is Dictionary<int, string> 

Console.WriteLine(JsonSerializer.Serialize(dic2));

record Product(int Id, string Name);