System.Text.Json: Sort by key Hashtable?

Question

I am serializing my object using a simple:

var options = new JsonSerializerOptions { WriteIndented = true, IncludeFields = true};
string jsonString = JsonSerializer.Serialize(obj, options);
File.WriteAllText("output.json", jsonString);

However my hierarchy contains a Hashtable. I'd like to have the Hashtable content be written in a consistent manner: always order by Keys (key is string in my case).

How can I do that in .NET 5 ?

My question is about Hashtable content and is no way related to ordering of class fields.

I cannot simply change the type of Hashtable to SortedDictionary since this would break all my existing BinaryFormatter serialized streams.

Use a `SortedDictionary`. The serializer will simply serialize the data in the order it's given by the collection, so you need to pick the right collection — Charlieface, Sep 22 '22 at 09:31

score 4 · Accepted Answer · answered Sep 22 '22 at 09:31

You could use a property as a pass-through:

    [JsonIgnore]
    public Hashtable MyHashtable { get; set; }
    
    [JsonPropertyName("MyHashtable")]
    public SortedDictionary<string, string> MyHashtableSorted 
    {
        get => new SortedDictionary<string, string>(
                     MyHashtable
                     .Cast<DictionaryEntry>()
                     .ToDictionary(x => (string)x.Key, x => (string)x.Value)
                );
        set {
            MyHashtable = new Hashtable();
            foreach (var x in value)
                MyHashtable.Add(x.Key, x.Value);
        }
    }

Or just use a SortedDictionary as your property type to start with...

Vivien P · Answer 2 · 2022-09-22T09:18:05.210

microsoft gives this advice to order as you want your object properties

using System.Text.Json;
using System.Text.Json.Serialization;

namespace PropertyOrder
{
    public class WeatherForecast
    {
        [JsonPropertyOrder(-5)]
        public DateTime Date { get; set; }
        public int TemperatureC { get; set; }
        [JsonPropertyOrder(-2)]
        public int TemperatureF { get; set; }
        [JsonPropertyOrder(5)]
        public string? Summary { get; set; }
        [JsonPropertyOrder(2)]
        public int WindSpeed { get; set; }
    }

    public class Program
    {
        public static void Main()
        {
            var weatherForecast = new WeatherForecast
            {
                Date = DateTime.Parse("2019-08-01"),
                TemperatureC = 25,
                TemperatureF = 25,
                Summary = "Hot",
                WindSpeed = 10
            };

            var options = new JsonSerializerOptions { WriteIndented = true };
            string jsonString = JsonSerializer.Serialize(weatherForecast, options);
            Console.WriteLine(jsonString);
        }
    }
}
// output:
//{
//  "Date": "2019-08-01T00:00:00",
//  "TemperatureF": 25,
//  "TemperatureC": 25,
//  "WindSpeed": 10,
//  "Summary": "Hot"
//}

But that's a class (`WeatherForecast`), not a `Hashtable` as requested by OP — knittl, Sep 22 '22 at 09:28

System.Text.Json: Sort by key Hashtable?

2 Answers2