Native AOT Support for MAUI

When using Native AOT with .NET MAUI, several requirements will need to be met to ensure the application works in release mode, explicitly on iOS and Mac Catalyst.

1. Implement compiled models for Entity Framework Core.
2. Implement source generation in System.Text.Json.
3. Enable the Interpreter for iOS and Mac Catalyst.

The following are basic instructions on how to fulfill these requirements. However, you should consult the official documentation (linked above) for each requirement.

Compiled models

To enable compiled models in your MAUI project:

1. Move your DbContext and models to a separate library that targets net8.0.

2. Create a dummy project with a project reference to the library. This will act as a startup project for the EF Core Tools we will run later. This can be as simple as a console application.

3. Implement an IDesignTimeDbContextFactory for your context. This can be placed in your dummy project. For example:

   internal class MyContextFactory : IDesignTimeDbContextFactory<MyContext>
   {
     public MyContext CreateDbContext(string[] args)
     {
        var optionsBuilder = new DbContextOptionsBuilder<MyContext>();
        optionsBuilder.UseSqlite("Data Source=:memory:");
        return new MyContext(optionsBuilder.Options, new HttpClientOptions()); 
     }
   }

4. Ensure you have the EF Core Tools installed.

5. Run the following command (appropriately adjusted for your situation):

   Optimize-DbContext \
      -OutputDir Models \
      -Context MyContext \
      -StartupProject MyDummyProject \
      -Project MyLibraryProject \
      -Namespace MyLibraryProject.Models

   Type this command on a single line. This should generate the compiled models in the specified output directory. We will be interested in the class named MyContextModel later.

6. In your MauiProgram.cs file, add the following statement as the first statement in the CreateMauiApp() method:

   AppContext.SetSwitch("Microsoft.EntityFrameworkCore.Issue31751", true);

   This addresses a deadlock issue in the compiled model initialization.

7. In your DbContext configuration, use the following statement:

   options.UseModel(MyContextModel.Instance);

   Your DbContext initialization should look something like this:

   mauiAppBuilder.Services.AddDbContext<MyContext>((sp, options) => 
   {
     options.UseSqlite(sp.GetRequiredService<SqliteConnection>());
     options.UseModel(MyContextModel.Instance);
   });

Source generation for System.Text.Json

Create a new partial class that inherits from JsonSerializerContext. It should look like this:

[JsonSerializable(typeof(Page<TodoItem>))]
[JsonSerializable(typeof(Page<Category>))]
[JsonSourceGenerationOptions(
  PropertyNameCaseInsensitive = true,
  PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase,
  DictionaryKeyPolicy = JsonKnownNamingPolicy.CamelCase,
  UseStringEnumConverter = true,
  WriteIndented = false,
  GenerationMode = JsonSourceGenerationMode.Metadata,
  AllowTrailingCommas = true,
  DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault,
  Converters = [
    typeof(JsonStringEnumConverter),
    typeof(DateTimeConverter),
    typeof(DateTimeOffsetConverter),
    typeof(TimeOnlyConverter),
    typeof(SpatialGeoJsonConverter)
  ]
)]
public partial class MySerializerContext : JsonSerializerContext
{
}

Add a JsonSerializable attribute for each entity that is stored in your DbContext similar to the ones in the example above. Finally, install the modified JsonSerializerContext in the MauiProgram.cs as the second statment in the CreateMauiApp function:

DatasyncSerializer.JsonSerializerOptions.TypeInfoResolver = MySerializerContext.Default;

Enable the Interpreter

Add the following property to the iOS release configuration in your MAUI app project file:

<MtouchInterpreter>all</MtouchInterpreter>

The property group should look something like the following:

<PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|net8.0-ios|AnyCPU'">
  <OptimizePNGs>true</OptimizePNGs>
  <MtouchInterpreter>all</MtouchInterpreter>
</PropertyGroup>

Having problems

Unfortunately, the development team does not have much experience with releasing iOS applications, so is of limited help. While you can add a discussion, you will probably get more assistance in the MAUI and Entity Framework Core projects.