Workarounds for Xamarin.iOS app with EFCore 2.0

[bricelam]

Updated to current known issues and workarounds:

• For Xamarin.Android, use package.config instead of PackageReference (dependent on System.Runtime.CompilerServices.Unsafe linked away in release leading to crashes android#1196).
• For Xamarin.Android, try changing AndroidLinkMode to SdkOnly ( EFCore SQLite - Android - Error constructor call failed efcore#11027 (comment)) or other workarounds to preserve additional reflection metadata, e.g. [assembly: Preserve (typeof (System.Linq.Queryable), AllMembers = true)] (dependent on Xamarin requires linker hints to preserve APIs accessed via reflection efcore#10963) or using a LinkDescription.xml file.
• For SQLite, use SQLitePCL.Batteries_V2.Init() (see https://github.com/ericsink/SQLitePCL.raw/wiki/SQLitePCL.Batteries.Init).
• Tooling is blocked on the fact that the linker used by Xamarin removes assembly level attributes (see Xamarin.iOS linker removes assembly attributes, but large & useful libraries (e.g. EF Core 2.0) rely on such being preserved macios#3655).

Good sample app link applying workarounds by @cwrea: https://github.com/cwrea/XamarinTodo/tree/master

Original Issue:

From @alexdrl on November 21, 2017 8:44

A Xamarin.iOS app with EFCore 2.0 needs a call to

SQLitePCL.Batteries_V2.Init();

If the call is not made, the app initialization throws this error message.

You need to call SQLitePCL.raw.SetProvider(). If you are using a bundle package, this is done by calling SQLitePCL.Batteries.Init().

Like explained here

Steps to reproduce

Xamarin.iOS project working with EFCore 2.0. Solution with a common .NET Standard project which shares code between iOS and Android, using PackageReference.

Further technical details

EF Core version: 2.0.0
Database Provider: Microsoft.EntityFrameworkCore.Sqlite
Operating system: iOS
IDE: Visual Studio 15.4

Copied from original issue: dotnet/efcore#10361

[bricelam]

Correct. I don't think Xamarin.iOS can handle the Assembly.Load() call. And binding directly to SQLitePCLRaw.batteries_v2.dll will cause problems if you're not using a bundle.

[bricelam]

From @alexdrl on November 22, 2017 18:27

I use the SQLitePCLraw assembly that gets added as a transitive dependency, and call that Init method, the app works correctly. In the project assets json, the Xamarin.iOS SQLitePCLraw package gets restored correctly.

[bricelam]

We should probably document this on the Supported .NET Implementations page or thereabouts.

[bricelam]

From @alexdrl on November 22, 2017 18:31

The documentation already stated that there are problems in Xamarin.iOS but there is no page that describes this (or other) workarounds.

[cwrea]

Worth noting here, with respect to the Entity Framework Core 2.1 release, and the Visual Studio 15.7.3 releases of Xamarin.iOS and Xamarin.Android:

• Xamarin.iOS apps using EF Core 2.1 won't build: iOS app build fails when referencing package (e.g. Entity Framework Core 2.1) that depends on newer System.Memory macios#4168.

• Xamarin.Android apps using EF Core 2.1 can't use linking: Android app build fails during "SdkOnly" linking when referencing package (e.g. Entity Framework Core 2.1) that depends on newer System.Memory android#1813.

At present, the only known workaround for Xamarin mobile app developers wishing to use Entity Framework Core is to not upgrade to the 2.1 release. i.e. Stay on 2.0.3 until the underlying Xamarin platforms have addressed deficiencies related to the new System.Memory 4.5 dependency that was introduced (indirectly) as part of the newer packages that EF Core 2.1 now depends on. I am not aware of any timeline with respect to when these issues may be fixed.

[dfoulk]

@cwrea Thank you for mentioning this. I would've spent hours debugging that issue if I hadn't seen your comment first! Literally saved us hundreds of dollars!

[cwrea]

@dfoulk You're welcome. FWIW, since I posted that, there's hope that Visual Studio 15.8 Preview 3 may address these issues. See my comment from a couple of days ago at dotnet/macios#4168 (comment) ... I haven't tried the preview myself, yet. Tied up in other project work at the moment.

[Pinox]

@cwrea very weird. I'm running ef core 2.1 on my android and native UWP and it works and builds fine (debug and release) , but I'm using Microsoft.Extentions.primitives version 2.0

[cwrea]

@Pinox Do you have linking enabled? The oustanding Android issue is specific to having linking enabled.