C#•3y ago

Custom JSON serializer not working

Hello I have a custom serializer i cannot get to work. When I use the model in a controller, it just gives me null. It is the following class I try to serialize

public class ExternalId
{
    public string Id { get; set; }
}

public class ExternalId
{
    public string Id { get; set; }
}

I want to be able to use the following input

{
    "id1": "a",
    "id2": "b",
    "id3": "3"
}
// to e.g. this class
public class MyDTO {
    public ExternalId Id1 {get; set;}
    public ExternalId Id2 {get; set;}
    public ExternalId Id3 {get; set;}
}

{
    "id1": "a",
    "id2": "b",
    "id3": "3"
}
// to e.g. this class
public class MyDTO {
    public ExternalId Id1 {get; set;}
    public ExternalId Id2 {get; set;}
    public ExternalId Id3 {get; set;}
}

This is my serializer. Is should just take the string, and wrap it in a ExternalId I have tried to put break points in here also, but they are never reached

public class ExternalIdSerializer : JsonConverter<ExternalId>
{
    public override ExternalId? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return reader.GetString() is null
            ? null
            : new ExternalId(reader.GetString()!);
    }

    public override void Write(Utf8JsonWriter writer, ExternalId externalId, JsonSerializerOptions options)
    {
        writer.WriteStringValue(externalId.Id);
    }
}

public class ExternalIdSerializer : JsonConverter<ExternalId>
{
    public override ExternalId? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return reader.GetString() is null
            ? null
            : new ExternalId(reader.GetString()!);
    }

    public override void Write(Utf8JsonWriter writer, ExternalId externalId, JsonSerializerOptions options)
    {
        writer.WriteStringValue(externalId.Id);
    }
}

And last, this is where I add my serializer

services
    .AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.PropertyNameCaseInsensitive = true;
        
        var converters = options.JsonSerializerOptions.Converters;
        converters.Add(new JsonStringEnumConverter());
        converters.Add(new ExternalIdSerializer());
    });

services
    .AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.PropertyNameCaseInsensitive = true;
        
        var converters = options.JsonSerializerOptions.Converters;
        converters.Add(new JsonStringEnumConverter());
        converters.Add(new ExternalIdSerializer());
    });

4 Replies

D.Mentia•3y ago

Not sure I understand the intent, and idk the problem. But just in case you aren't aware and it might help you, you can natively serialize to a Dictionary<string,string> or <string,object>, if you have some arbitrary keys that you don't know ahead of time Newtonsoft also has an attribute to put all keys not defined on the model into such a dictionary

Doombox•3y ago

that JSON Converter looks a lot like a System.Text.JSON one, do they share the same base class?

ArkobatOP•3y ago

Ohh, didn't realise they were called the same... I can see its using System.text 😦 So, I hav removed Newtonsoft from my project, and is now using Sytem.Text everywhere. However, I still see the same problem. I have updated my code examples to show what I do.

Doombox•3y ago

IndentedJsonOptions = new JsonSerializerOptions(JsonSerializerDefaults.General)
{
  WriteIndented = true,
  Converters = { new TypeJsonConverter() }
};
// ...
await JsonSerializer.DeserializeAsync<T>(filestream, IndentedJsonOptions);

IndentedJsonOptions = new JsonSerializerOptions(JsonSerializerDefaults.General)
{
  WriteIndented = true,
  Converters = { new TypeJsonConverter() }
};
// ...
await JsonSerializer.DeserializeAsync<T>(filestream, IndentedJsonOptions);

is how I've done it I don't know how you'd do it with your services registration though

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Custom JSON serializer not working