Jsonserializer and record types with "primary" constructor (original) (raw)

I've been playing with the new C# 9.0 features to evaluate how they integrate with ASP.NET Core. As part of that, I've been checking records and I found that the deserializer throws if I try to deserialize a record defined as follows:

public record TodoTask(string Description);

}

The exception thrown is:

   at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_ConstructorParameterIncompleteBinding(ConstructorInfo constructorInfo, Type parentType)
   at System.Text.Json.Serialization.Converters.ObjectWithParameterizedConstructorConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCoreAsObject(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
   at System.Text.Json.JsonSerializer.ReadAsync[TValue](Stream utf8Json, Type returnType, JsonSerializerOptions options, CancellationToken cancellationToken)

This forces people to use the longwinded syntax for records when writing APIs, which is something we want to avoid. The closest I got is to do, which is far more verbose:

public record TodoTask
{
    public TodoTask(string description) => Description = description;
    public string Description { get; init; }
}