How to ignore JsonPropertyName in serialization using System.Text.Json in .Net 6

Question

I am using System.Text.Json in .NET 6 and I have some data classes that have properties annotated with JsonPropertyName to be able to communicate with another API, but now I need to use the original properties names for another business reason and was looking for a way to make the serializer ignore those annotations and use the actual property names. I've found that in Newtonsoft I could've used ContractResolver to do it like suggested here, but I couldn't find an alternative in System.Text.Json. Now I am thinking of using DTOs to do it but I am looking for a simpler solution if it's available.

Here's a quick example, say we have this Account class:

public class Account {
    [JsonPropertyName("fname")]
    public string FirstName { get; set; }
    [JsonPropertyName("lname")]
    public string LastName { get; set; }
    [JsonPropertyName("years_old")]
    public int Age {get; set; }
}

In one use I want the response sent to be of the format:

{
    "fname": "John",
    "lname": "Doe",
    "years_old": 25
}

And in another response, I need:

{
    "firstname": "John",
    "lastname": "Doe",
    "age": 25
}

Now this is just a sample, but my actual classes have a lot of properties, and making DTOs isn't for each use case is too much work. Hence why I am looking for a solution using something like Newtonsoft DefaultContractResolver but using System.Text.Json.

PS: I can't afford to move back to Newtonsoft.Json.

@Serge I explicitly said that I needed those for other requests, so removing them isn't really an option. I was looking for some way to disable them for a given serialization. — Isu, Jun 09 '23 at 11:46
Your question is not clear. There are two operations - serialization and deserialization. What do you need what for? — Serge, Jun 09 '23 at 11:49
The class is used in communication with 2 different APIs, where in one it needs to use properties names defined using the `JsonPropertyName`, whilst the other requires the actual properties names. Something like what's required in the question I linked. — Isu, Jun 09 '23 at 11:56
Data from API usually needs to be deserialized only. In any case it is getting even more confused now. — Serge, Jun 09 '23 at 12:01
I think it's better to create two classes of Account, with fields that API's required. And then implement some basic logic to clone/copy one class to another if needed. If it's different API's with a different fields names, at one point you will require to pass some additional field to one of them, but not for another. — dima_horror, Jun 09 '23 at 13:45
In .NET 7 MSFT introduced `DefaultJsonTypeInfoResolver` which is equivalent to `DefaultContractResolver`, see [System.Text.Json API is there something like IContractResolver](https://stackoverflow.com/a/74284215/3744182). You could cancel the `JsonPropertyNameAttribute` using that. See e.g. [Asymmetric Field Names for serialisation and deserialisation using System.Text.Json](https://stackoverflow.com/q/76250152/3744182). But in .NET 6 your options are much more limited. Can you more to .NET 7? — dbc, Jun 10 '23 at 19:18
@dbc I reached the same conclusion too in my research, before deciding on doing anything I thought I'd ask here to check if there is maybe some way to do it in .NET 6 but sadly there doesn't seem to be any. — Isu, Jun 10 '23 at 19:35
There's nothing easy. Obviously you could create your own custom converter that cycles through the properties and serializes each one using reflection. — dbc, Jun 10 '23 at 19:38

Serge · Answer 1 · 2023-06-09T13:40:56.480

If you don't want to use a mapper and dto, the only way I see ( and I think it is more effective)

    var origJson = @"{
    ""fname"": ""John"",
    ""lname"": ""Doe"",
    ""years_old"": 25
}";

    var fixedJson = FixPropertyNames(origJson);

public string FixPropertyNames(string json)
{
    StringBuilder sb = new StringBuilder(json);

    sb.Replace("\"fname\"", "\"firstname\"");
    sb.Replace("\"lname\"", "\"lastname\"");
    sb.Replace("\"years_old\"", "\"age\"");

    return sb.ToString();
}

or if your classes are small, you can remove a string builder and put all code in one line.

fixedJson= origJson.Replace("\"fname\"", "\"firstname\"").Replace("\"lname\"", "\"lastname\"").Replace("\"years_old\"", "\"age\"");

And I guess your API should return a content, since you have created a json string already

 return Content(jsonString, "application/json");

How to ignore JsonPropertyName in serialization using System.Text.Json in .Net 6

1 Answers1