Nullables in Entity Framework Core on Xamarin iOS

Question

We are developing an Mobile app using Xamarin.Forms, which is backed by a Web app using ASP.NET Core. We load various models from databases on both the Web and Mobile apps, and recently we have transitioned to using EntityFramework Core (will refer to as EFCore) on the Web app.

We are currently looking at transitioning the Mobile app to also use the EFCore to allow us to share more code between the apps, but have run into problems with EFCore on iOS. It seems able to compile and run, and can load simple models, but fails to load nullable types which are used to specify optional relationships between models. This person seems to have EFCore running in iOS and provides a project for their code. I have pulled and ran the project myself to check it works, which it did, but after adding a nullable relation to his simple model, it subsequently failed to both load and create an item with this error:

System.ExecutionEngineException: Attempting to JIT compile method '(wrapper runtime-invoke) :runtime_invoke_void__this___int_byte_byte_byte_byte_byte_object_object_object_object_object_object_object_object_object_object_Nullable1 (object,intptr,intptr,intptr)' while running in aot-only mode. See https://developer.xamarin.com/guides/ios/advanced_topics/limitations/ for more information.

This error does not occur when running on the simulator, only on a device.

My question is whether anyone has had any success with getting Nullables working with EFCore on Xamarin iOS?

Many thanks, Will.

P.S. We are open to changing EFCore/Xamarin.iOS/Mono version to solve the problem.

You might be hitting this github.com/aspnet/EntityFramework/issues/9249 — Smit
– Smit, Commented Aug 10, 2017 at 0:52
This also looks related bugzilla.xamarin.com/show_bug.cgi?id=58424 This issue is a blocking point for our project. — TomTom
– TomTom, Commented Aug 10, 2017 at 9:13
Yeah I found these two issues yesterday after posting. Currently in discussing it on the Xamarin Bugzilla. — William Gilmour
– William Gilmour, Commented Aug 11, 2017 at 11:57

Guillaume · Accepted Answer · 2017-08-29 09:47:12Z

2

+50

This is a known issue. iOS has some limitations on generics, nullables... because Apple disallow code generation at runtime.

The issue is referenced on github for entity framework : Xamarin iOS : Crash when i add row to table with nullable type or with a lot of columns

And on Xamarin's bugzilla : Bug 58424 - Xamarin iOS : EF Core crash when I add row to table with nullable type or with a lot of columns

answered Aug 29, 2017 at 9:47

Guillaume

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