Is AOT not supported for LINQ query expressions?

[ashok-kuvaraja]

I have developed two custom packages: one for generating item sources with data operation support, and another for displaying items similar to a ListView. The items source generation package uses reflection and LINQ expressions to perform data operations.

The issue arises when I enable AOT (Ahead-of-Time) compilation and generate the .ipa file—the app crashes. However, it works perfectly in both Release and Debug modes on the iOS platform. On macOS, it crashes in Release mode but runs fine in Debug mode.

I generated the .ipa file using the following command:

dotnet publish -f net9.0-ios -c Release -p:BuildIpa=True -p:EnableCodeSigning=false

Upon investigation, I found documentation indicating that LINQ has limitations with AOT compilation. Specifically, it mentions that certain LINQ features are not supported under AOT.

Documentation Reference:
EF Core Native AOT and Precompiled Queries - Limitations

Can anyone confirm whether LINQ is currently unsupported with AOT, or if there are workarounds available?

[Dreamescaper]

Are you using EF Core?
Or simply LINQ to objects?

[ashok-kuvaraja]

Thanks for the response. I apply LINQ to the objects.

[Dreamescaper]

LINQ to object DOES support AOT.
(EF Core does not, but you're not using it apparently)

Reflection, however, can cause issues with AOT. You can read here:
https://learn.microsoft.com/en-us/dotnet/core/deploying/trimming/fixing-warnings

[ashok-kuvaraja]

As I mentioned earlier in this post, I have two packages—one for source work and another for layout work. I’ve added the source package as a dependency to the layout package. I’ve enabled AOT (Ahead-of-Time compilation) for the sample and layout packages only, not for the source package. The source package contains reflection-based code.

My question is: Will the MAUI framework trim the reflection code in the source package even if AOT is not enabled for it?

[Dreamescaper]

You can't enable AOT selectively, if the project is compiled with AOT - all its dependencies are compiled with AOT as well (it's not MAUI specific, but applies for any .net project).

[ashok-kuvaraja]

@Dreamescaper - Thanks for the clarifications.

[jonathanpeppers]

I think there is probably some confusion here, as to what flavor of AOT you're using.

• NativeAOT (what you linked to) is only enabled when setting -p:PublishAot=true
  • Has limitations, requirements of solving trimmer warnings
• Default release mode, iOS build uses Mono AOT
  • Should have fewer limitations, that are more related to the iOS platform than AOT.

Which AOT are you using? Mono's AOT or NativeAOT?

To track down this further, what is the crash? Do you have a stack trace?

[ashok-kuvaraja]

@jonathanpeppers - I am using NativeAOT. I am unable to get stack trace details because the application closes without leaving any information.

Would it be possible to retrieve the stack trace of a crash in release mode?

[jonathanpeppers]

Yes, there is an old doc here, Xcode Organizer should let you see the console output:

• https://learn.microsoft.com/en-us/xamarin/ios/deploy-test/debugging-in-xamarin-ios?tabs=macos#accessing-the-console

[vitek-karas]

Since you're using NativeAOT - when you publish the app, do you get any warnings reported? As Jonathan mentioned above, NativeAOT requires you to make the app compatible with trimming/NativeAOT - the compiler will report any incompatibilities via warnings.