C#•2y ago

✅ System.Text.Json serialization problem

hello, I am using System.Text.Json. I have a struct that has 2 properties: a bool IsDefined and a T value. IsDefined gets set to true when value gets set. This is a container for properties that don't necessarily need to be set, but if they are set, they will get included in the serialization. The problem is that in the Write method, STJ automatically writes out the property name, which results in this Json if only the name property is set: {"name":"lol","parent_id":"position":}. The STJ write method:

        if (!value.IsDefined) return;

        switch (value.Value)
        {
            case long:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            case ulong:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            default:
                writer.WriteRawValue(JsonSerializer.Serialize(value.Value));
                break;
        }

        if (!value.IsDefined) return;

        switch (value.Value)
        {
            case long:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            case ulong:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            default:
                writer.WriteRawValue(JsonSerializer.Serialize(value.Value));
                break;
        }

How can I get around this?

121 Replies

Anu6is•2y ago

https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/ignore-properties?pivots=dotnet-7-0

Sh1be•2y ago

this sadly doesn't work for my use case because it works like this: - value set - value is a normal value --> serialize - value null / default --> serialize - value not set --> don't serialize I want to check whether .IsDefined is true. how would I be able to do that?

deluvas•2y ago

https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/converters-how-to?pivots=dotnet-7-0 you could write a own jsonconverter for that class and use it with the system.text.json jsonserializer, then you could handle yourself how you want it to behave

Sh1be•2y ago

I have that right now

internal class IgnorableConverter<T> : JsonConverter<Ignorable<T>>
{
    public override Ignorable<T> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }

    public override void Write(Utf8JsonWriter writer, Ignorable<T> value, JsonSerializerOptions options)
    {
        if (!value.IsDefined) return;

        switch (value.Value)
        {
            case long:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            case ulong:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            default:
                writer.WriteRawValue(JsonSerializer.Serialize(value.Value));
                break;
        }
    }
}

internal class IgnorableConverter<T> : JsonConverter<Ignorable<T>>
{
    public override Ignorable<T> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }

    public override void Write(Utf8JsonWriter writer, Ignorable<T> value, JsonSerializerOptions options)
    {
        if (!value.IsDefined) return;

        switch (value.Value)
        {
            case long:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            case ulong:
                if (value.Value != null) writer.WriteStringValue(value.Value.ToString());
                else writer.WriteNullValue();
                break;

            default:
                writer.WriteRawValue(JsonSerializer.Serialize(value.Value));
                break;
        }
    }
}

but if it gets into the Write method the property name will automatically be written out.

    [JsonPropertyName("name")]
    public Ignorable<string> Name { get; init; }

    [JsonPropertyName("parent_id")]
    public Ignorable<ulong?> ParentId { get; init; }

    [JsonPropertyName("position")]
    public Ignorable<uint> Position { get; init; }

    [JsonPropertyName("name")]
    public Ignorable<string> Name { get; init; }

    [JsonPropertyName("parent_id")]
    public Ignorable<ulong?> ParentId { get; init; }

    [JsonPropertyName("position")]
    public Ignorable<uint> Position { get; init; }

if only name is set and the other ones arent, they will still get into the Write method and will automatically write out the parent_id: for example which i dont want. can i change this behaviour somehow?

deluvas•2y ago

var serializeOptions = new JsonSerializerOptions
{
    WriteIndented = true,
    Converters =
    {
        new DateTimeOffsetJsonConverter()
    }
};

jsonString = JsonSerializer.Serialize(weatherForecast, serializeOptions);

var serializeOptions = new JsonSerializerOptions
{
    WriteIndented = true,
    Converters =
    {
        new DateTimeOffsetJsonConverter()
    }
};

jsonString = JsonSerializer.Serialize(weatherForecast, serializeOptions);

do you also tell your jsonserializer to use that converter?

Sh1be•2y ago

yes

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✅ System.Text.Json serialization problem