[Question] In which cases JsonConvert.DeserializeObject<T>(string, JsonSerializerSettings) actually returns null?

I’m working with .NET core 3.1, C# 8 and nullable reference types enabled.

From the class library I’m writing, I’m referencing the version 12.0.3 of Newtonsoft JSON.

I noticed that, by calling JsonConvert.DeserializeObject<T>(string, JsonSerializerSettings?), I can get a null reference (Visual Studio analyzers detect a possible dereferencing of a null reference).

Notice that I’m calling the overload which takes a string and an instance of JsonSerializerSettings. I’m only using the JsonSerializerSettings in order to handle the possible deserialization errors (via the Error property).

The github source code confirms that the overload I’m calling can possible return a null reference, via the MaybeNull attribute: take a look here for a confirmation.

My question is: in which cases newtonsoft JSON returns a null reference when deserializing a JSON string to a .NET type ?

Usually it returns an object of the given type populated or having its properties at the default value for their type, I have never encountered a case where null is returned instead.

[lechu445]

@EnricoMassone you are right, thank you for the answer.

In RFC 7159 there is such definition:

JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays).

so, null, 1, "text", true are all valid JSONs.

[TylerBrinkley]

I think the single string parameter overload just got missed when the library was annotated.

I’d imagine with custom converters you could conceivably return null from a non "null" input as well.