Allowing customization of JSON key ordering when serializing dictionaries

Source type

Dictionary<string, int> // for example, with ("a", 1), ("c", 2), and ("b", 3), added in that order.

Desired JSON

{"a":1,"b":3,"c":2}

Actual JSON

{"a":1,"c":2,"b":3}

Steps to reproduce

void Main() // in linqpad
{
    var d = new Dictionary<string, int>
    {
        ["a"] = 1,
        ["c"] = 2,
        ["b"] = 3,
    };
    var s = new JsonSerializerSettings
    {
        ContractResolver = new OrderedPropertyNamesContractResolver(StringComparer.OrdinalIgnoreCase),
    };
    JsonConvert.SerializeObject(d).Dump(); // yields {"a":1,"c":2,"b":3}, as expected.
    JsonConvert.SerializeObject(d, s).Dump(); // yields the same, but was hoping for {"a":1,"b":3,"c":2}
}

// My very naive attempt at doing this without constructing a whole new SortedDictionary or SortedList ---
class OrderedPropertyNamesContractResolver : DefaultContractResolver
{
    readonly IComparer<string> Comparer;

    public OrderedPropertyNamesContractResolver(IComparer<string> comparer) => Comparer = comparer ?? throw new ArgumentNullException(nameof(comparer));

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var properties = base.CreateProperties(type, memberSerialization).OrderBy(property => property.PropertyName, Comparer).ToList();
        foreach (var (property, index) in properties.Select(ValueTuple.Create<JsonProperty, int>))
        {
            property.Order = index;
        }
        return properties;
    }
}

Current workaround

Construct a SortedDictionary or SortedList with the same entries as the source dictionary, and then serialize that. Possibly insufficient when the dictionary is actually inside an aggregate that you’re serializing.

[robheffo79]

I personally would like to see this added. I am using Json serialisation to produce a “normalised” versions of arbitrary objects. Being able to ensure Dictionarys have consistantly ordered keys helps greatly because a dictionary doesn’t care about the order, just that a key is present or not, whereas the normalisation process does care about both the order and whether or not a key is present…

[rummelsworth]

• (a) Agreed, as mentioned above.
• (b) Agreed, but irrelevant as discussed above.
• © Agreed, but the workaround is partial, as mentioned above.

No offense taken. I think it’s great you engaged with this. At the very least, our discussion has been a “smoke test” of the feature’s reasonableness. Thanks.