Cannot apply attribute class 'JsonConverter' because it is abstract

Question

I'm using Newtonsoft JSON library and I'm trying to deserialize a JSON. The problem is that when I use [JsonConverter(typeof(StringEnumConverter))] I get this error: Cannot apply attribute class 'JsonConverter' because it is abstract.

Here are my classes:

 public class ActionRepository { [JsonConverter(typeof(StringEnumConverter))] public enum AllowedActions { FINDWINDOW, } public enum AllowedParameters { WINDOWNAME, } } public class Action { public AllowedActions Name { get; set; } public List<Parameter> Parameters { get; set; } }

I get the squiggly line under the JsonConverter.

EDIT: The JsonConverter class is indeed abstract if I navigate to the class (ctrl+click in VS). I'm using .NET for Windows Universal.

[JsonConverter(typeof(StringEnumConverter))] doesn't apply an attribute of type JsonConverter, it applies the attribute JsonConverterAttribute which is not abstract. — dbc
– dbc, Commented Apr 18, 2019 at 16:43
From the c# language spec: Attributes: By convention, attribute classes are named with a suffix of Attribute. An attribute_name of the form type_name may either include or omit this suffix. If an attribute class is found both with and without this suffix, an ambiguity is present, and a compile-time error results. So it's odd that the IDE somehow thought JsonConverter was being applied rather than JsonConverterAttribute. Possibly an IDE bug here? — dbc
– dbc, Commented Apr 18, 2019 at 16:43

TomSelleck · Accepted Answer · 2019-04-18 14:56:32Z

2

The problem appears to be that when not targeting a .Net framework application - the JsonConverter class is marked as abstract.

The solution looks to be to use JsonConvert as an alternative.

answered Apr 18, 2019 at 14:56

TomSelleck

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1 Comment

Mike Christensen Over a year ago

Silly idea, but since it's abstract what if you just make your own subclass and use that?

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