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Asked: 2026-06-01T15:11:37+00:00

I’m writing some code that will serialize a C# object to JSON, send it

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I’m writing some code that will serialize a C# object to JSON, send it over the wire and deserialize the JSON to a Python object.

The reverse will also be done, i.e. serialize a Python object to JSON, send it over the wire and deserialize the JSON to a C# object.

On the C# side, I use the ServiceStack JSON libraries. In Python, I’m using the built-in json libraries. The C# library can be changed easily if necessary, the Python one far less so. 


// C#
var serializer = new JsonSerializer();
var json = serializer.SerializeToString(request);

// Python
// JsonCodec inherits from JSONEncoder and hooks to 'default' and just 
// returns obj.__dict__ where obj is the object to be serialized
actualSerializedResponse = JsonCodec().encode(response)

I’ve written a unit test in C# to verify that the ServiceStack serialized JSON is as expected by the Python side. In the test, an instance of Foo is created, populated with some hardcoded values, then serialized. To ensure validity, I compare the serialized JSON to some JSON saved in a file, where the contents of the file represent what the Python side expects.

Similarly, there’s a unit test in Python to verify that the built-in json library’s serialized JSON is as expected by the C# side. Again, to ensure validity, I compare the actual serialized JSON to some JSON saved in a file.

In both cases, the fact that I’m comparing the serialized JSON to some JSON saved in a file implies that the order in which properties are serialized to JSON must be consistent every time and every where the tests are run.

My questions:

  • In the C# unit test, it seems that the order of the properties in the JSON match the order in which the properties were defined in the C# class whose instance is being serialized. Can this be relied on?

  • In the Python unit test, the order of the properties is consistent but arbitrary. This makes sense since it relies on dict and the Python dictionaries are unordered. But can this be relied every time/where?

  • Is there a better way to do all this?

Many thanks in advance.

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1 Answer

  1. Editorial Team

    Regarding the Python side: you can pass the JSON decoder an option to use an “ordered dictionary” (requires python 2.7 however):

    from http://docs.python.org/library/json.html#json.load:

    object_pairs_hook is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs. The return value of object_pairs_hook will be used instead of the dict. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, collections.OrderedDict() will remember the order of insertion). If object_hook is also defined, the object_pairs_hook takes priority.

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