The polymorphism in C# with Newtonsoft.Json is unable to deserialize child classes due to the JsonConverter annotation present in the child class.

[npottiez]

"Adding [JsonConverter(typeof(JsonSubtypes), "{{{discriminatorName}}}")] to the child C# class compels Newtonsoft to not look at the subtypes within the child class. To do it properly, one should move the line [JsonConverter(typeof(JsonSubtypes), "{{{discriminatorName}}}")] in {{#mappedModels.length}}.
like this ?
{{#mappedModels.length}}
[JsonConverter(typeof(JsonSubtypes), "{{{discriminatorName}}}")]
{{/mappedModels.length}}

https://github.com/OpenAPITools/openapi-generator/blame/275ed9296dea4a1a894cc5b3402b5b8f3a61e7d7/modules/openapi-generator/src/main/resources/csharp/modelGeneric.mustache#L13

[wing328]

can you please file a PR with the suggested fix?

[DaveK-Rocketmakers]

I've been hit by this issue recently. Raised #19972 with an adaption on the suggested change.