Json POCO mapping and type hierarchy

[forik]

Hello, I have a table entity like this:

class Entity
{
    [Column(TypeName = "jsonb")]
    public BaseType Config {get;set;}
}

And a number of types derived from BaseType:

public class Derived1 : BaseType { public string StringProp {get;set;} }

public class Derived2 : BaseType { public int IntProp {get;set;} }

... etc you got the idea.

Is this possible to achieve?

I tried to configure a custom ValueConverter<BaseType, JsonDocument> and conversion to JsonDoument was easy.
Conversion from JsonDocument can be tricky as JsonDocument doesn't contain a ContainsKey method or similar but doable.

Missing part is querying as Where(x => ((Dervived)x.Config).IntProp == 1) couldn't be translated.

[roji]

This currently isn't supported out of the box, since it would require some strategy of storing the type inside the JSON document in some way (i.e. is it a Derived1 or a Derived2?). This is typically done by introducing some sort of discriminator property (like EF Core already does for Type-Per-Hierarchy mapping, see docs), but nothing like this is supported for JSON at the moment.

Some serious work on JSON is planned for EF Core 7.0 - I'll make sure we have this on our radar, though it definitely isn't a guarantee this would be supported for that version.

[roji]

Opened dotnet/efcore#27779 to track this on the EF Core side, closing here.