JsonConverterAttribute cannot be applied to an Enum

[Joelius300]

Since I'm trying to migrate from Newtonsoft.Json to the new System.Text.Json APIs, I have to be able to use a Enum-string converter.

In json.net you can do this really easily with this attribute on the enum.

[Newtonsoft.Json.JsonConverter(typeof(Newtonsoft.Json.Converters.StringEnumConverter))]

Since there is both a JsonConverterAttribute and a JsonStringEnumConverter class, I thought you would do it like this:

[System.Text.Json.Serialization.JsonConverter(typeof(System.Text.Json.Serialization.JsonStringEnumConverter))]

However after getting a compiler error I quickly realized that the JsonConverterAttribute can't even be used on an Enum because it only has the following three AttributeTargets-flags.

• AttributeTargets.Class
• AttributeTargets.Struct
• AttributeTargets.Property

Are you not supposed to use this attribute and converter like this?
Are there any samples because there I've not found any in the docs?

I was able to do configure this globally in asp.net core without using attributes like this:

services.AddControllers().AddJsonOptions(options => options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter()));

I supose you should be able to do the same passing the same options to your JsonSerializer

[Joelius300]

I tried that. These options won't get used globally when using JsonSerializer (which I fully understand) but also won't get used when using IJSRuntime (which is very surprising to me).
I need a way of ignoring null values for IJSRuntime which uses System.Text.Json and does not expose any possibilities to define options or customize the serializer. The first thought would be one of the JsonAttributes since these will be respected no matter from where and with what options the serializer gets called.

[steveharter]

This does look to be an oversight on this scenario. I'll bring up a PR soon on this and review it internally for consideration for 3.0.

cc @JeremyKuhne

[Joelius300]

Thank you @steveharter. Will this fix be available in one of the next previews and if so in which one? Or do you also do fixes that will only be released on the 3.0 stable release?

[karelz]

Fixed in master (5.0) in PR dotnet/corefx#39790 and also in release/3.0 branch (3.0) in PR dotnet/corefx#39812.