System.Text.Json.Serialization Order of serialized properties

[Jogge]

I'm missing an attribute for setting the order of the element in the JSON output.

Example:

I want the @SEGMENT to be the first element in the serialized JSON output of MyClass:

public abstract class MyBase
{
    [JsonPropertyName("@SEGMENT")]
    public virtual string Segment { get; set; } = "1";

    public int ID { get; set; }
}

public class MyClass : MyBase
{
    public string Name { get; set; }
}

The result when serializing MyClass is:

{
    "MyClass": {
    	"Name": "Foo",
    	"@SEGMENT": "1",
    	"ID": 42
    }
}

I would like the serialized JSON output to be:

{
    "MyClass": {
    	"@SEGMENT": "1",
    	"Name": "Foo",
    	"ID": 42
    }
}

or

{
    "MyClass": {
    	"@SEGMENT": "1",
    	"ID": 42,
    	"Name": "Foo"
    }
}

Json.NET has an attribute for this: https://www.newtonsoft.com/json/help/html/JsonPropertyOrder.htm

Related question: .NET core 3: Order of serialization for JsonPropertyName (System.Text.Json.Serialization)

[layomia]

From @Praveen-Rai in https://github.com/dotnet/corefx/issues/38669:

An attribute similar to JsonPropertyAttribute in JSON.Net or DataMemberAttribute in System.Runtime.Serialization.

[layomia]

From @ahsonkhan in https://github.com/dotnet/corefx/issues/38669:

This is an interesting feature request which we will consider for the future.

@steveharter, is it feasible for us to extend our existing attribute to enable this scenario in the future? We should make sure our current design allows for it.

[steveharter]

This feature was discussed early on but did not make the list for v1.

is it feasible for us to extend our existing attribute to enable this scenario in the future? We should make sure our current design allows for it.

We don't have an existing attribute - we'd need to create a new one (e.g. JsonPropertyOrderAttribute).

The existing design would support this well as we currently build and cache an array of the properties to serialize, and the ordering is currently determined by reflection order (which is not deterministic) which can be changes to support this new attribute.

[layomia]

Closing - duplicate of #728.