dotnet-native-aot

Imported from wshaddix/dotnet-skills (skills/dotnet-native-aot/SKILL.md). Install upstream with npx skills add wshaddix/dotnet-skills --skill dotnet-native-aot. Copyright stays with the author.

dotnet-native-aot

Full Native AOT compilation pipeline for .NET 8+ applications: PublishAot configuration, ILLink descriptor XML for type preservation, reflection-free coding patterns, P/Invoke considerations, binary size optimization, self-contained deployment with runtime-deps base images, and diagnostic analyzers (EnableAotAnalyzer/EnableTrimAnalyzer).

Version assumptions: .NET 8.0+ baseline. Native AOT for ASP.NET Core Minimal APIs and console apps shipped in .NET 8. .NET 9 improved trimming warnings and library compat. .NET 10 enhanced request delegate generator and expanded Minimal API AOT support.

Scope boundary: This skill owns general .NET Native AOT compilation -- the publish pipeline, MSBuild configuration, type preservation, P/Invoke, and size optimization. MAUI-specific iOS/Mac Catalyst AOT (publish profiles, platform-specific library compat) -- see [skill:dotnet-maui-aot]. AOT-first application design patterns (source gen over reflection, DI, serialization choices) are in [skill:dotnet-aot-architecture]. Trim-safe library authoring is in [skill:dotnet-trimming]. WASM AOT for Blazor/Uno is in [skill:dotnet-aot-wasm].

Out of scope: MAUI iOS/Mac Catalyst AOT pipeline -- see [skill:dotnet-maui-aot]. Source generator authoring (Roslyn API) -- see [skill:dotnet-csharp-source-generators]. DI container patterns -- see [skill:dotnet-csharp-dependency-injection]. Serialization depth -- see [skill:dotnet-serialization]. Container deployment orchestration -- see [skill:dotnet-containers].

Cross-references: [skill:dotnet-aot-architecture] for AOT-first design patterns, [skill:dotnet-trimming] for trim-safe library authoring, [skill:dotnet-aot-wasm] for WebAssembly AOT, [skill:dotnet-maui-aot] for MAUI-specific AOT, [skill:dotnet-containers] for runtime-deps base images, [skill:dotnet-serialization] for AOT-safe serialization, [skill:dotnet-csharp-source-generators] for source gen as AOT enabler, [skill:dotnet-csharp-dependency-injection] for AOT-safe DI, [skill:dotnet-native-interop] for general P/Invoke patterns and cross-platform library resolution.

PublishAot Configuration

Enabling Native AOT

<!-- App .csproj -->
<PropertyGroup>
  <PublishAot>true</PublishAot>
</PropertyGroup>

# Publish as Native AOT
dotnet publish -c Release -r linux-x64

# Publish for specific targets
dotnet publish -c Release -r win-x64
dotnet publish -c Release -r osx-arm64

MSBuild Properties: Apps vs Libraries

Apps and libraries use different MSBuild properties. Do not mix them.

For applications (console apps, ASP.NET Core Minimal APIs):

<PropertyGroup>
  <!-- Enable Native AOT compilation on publish -->
  <PublishAot>true</PublishAot>

  <!-- Enable analyzers during development (not just publish) -->
  <EnableAotAnalyzer>true</EnableAotAnalyzer>
  <EnableTrimAnalyzer>true</EnableTrimAnalyzer>
</PropertyGroup>

For libraries (NuGet packages, shared class libraries):

<PropertyGroup>
  <!-- Declare the library is AOT-compatible (auto-enables analyzers) -->
  <IsAotCompatible>true</IsAotCompatible>
  <!-- Declare the library is trim-safe (auto-enables trim analyzer) -->
  <IsTrimmable>true</IsTrimmable>
</PropertyGroup>

IsAotCompatible and IsTrimmable automatically enable the AOT and trim analyzers respectively. Do not also set PublishAot in library projects -- libraries are not published as standalone executables.

Diagnostic Analyzers

Enable AOT and trim analyzers during development to catch issues before publishing:

<PropertyGroup>
  <EnableAotAnalyzer>true</EnableAotAnalyzer>
  <EnableTrimAnalyzer>true</EnableTrimAnalyzer>
</PropertyGroup>

Analysis Without Publishing

Run analysis during dotnet build without a full publish:

# Analyze AOT compatibility without publishing
dotnet build /p:EnableAotAnalyzer=true /p:EnableTrimAnalyzer=true

# See per-occurrence warnings (not grouped by assembly)
dotnet build /p:EnableAotAnalyzer=true /p:EnableTrimAnalyzer=true /p:TrimmerSingleWarn=false

This reports IL2xxx (trim) and IL3xxx (AOT) warnings without producing a native binary, enabling fast feedback during development.

Common Diagnostic Codes

ILLink Descriptors for Type Preservation

When code uses reflection that the trimmer cannot statically analyze, use ILLink descriptor XML to preserve types. Do not use legacy RD.xml -- it is a .NET Native/UWP format that is silently ignored by modern .NET AOT.

ILLink Descriptor XML

<!-- ILLink.Descriptors.xml -->
<linker>
  <!-- Preserve all public members of a type -->
  <assembly fullname="MyApp">
    <type fullname="MyApp.Models.LegacyConfig" preserve="all" />
    <type fullname="MyApp.Services.PluginLoader">
      <method name="LoadPlugin" />
    </type>
  </assembly>

  <!-- Preserve an entire external assembly -->
  <assembly fullname="IncompatibleLibrary" preserve="all" />
</linker>

<!-- Register in .csproj -->
<ItemGroup>
  <TrimmerRootDescriptor Include="ILLink.Descriptors.xml" />
</ItemGroup>

[DynamicDependency] Attribute

For targeted preservation in code (preferred over ILLink XML for small, localized cases):

using System.Diagnostics.CodeAnalysis;

// Preserve a specific method
[DynamicDependency(nameof(LegacyConfig.Initialize), typeof(LegacyConfig))]
public void ConfigureApp() { /* ... */ }

// Preserve all public members
[DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(PluginBase))]
public void LoadPlugins() { /* ... */ }

When to Use Which

Reflection-Free Patterns

Native AOT works best with code that avoids runtime reflection entirely. Replace reflection patterns with compile-time alternatives.

See [skill:dotnet-aot-architecture] for comprehensive AOT-first design patterns.

P/Invoke Considerations

P/Invoke (platform invoke) calls to native libraries generally work with Native AOT, but require attention:

Direct P/Invoke (Preferred)

// Direct P/Invoke -- AOT-compatible, no runtime marshalling overhead
[LibraryImport("libsqlite3", EntryPoint = "sqlite3_open")]
internal static partial int Sqlite3Open(
    [MarshalAs(UnmanagedType.LPStr)] string filename,
    out nint db);

Use [LibraryImport] (.NET 7+) instead of [DllImport] -- it generates marshalling code at compile time via source generators, making it fully AOT-compatible.

DllImport vs LibraryImport

// Migrate from DllImport to LibraryImport
// Before:
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool CloseHandle(IntPtr hObject);

// After:
[LibraryImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static partial bool CloseHandle(IntPtr hObject);

Native Library Deployment

When publishing as Native AOT, native libraries (.so, .dylib, .dll) must be alongside the binary:

<ItemGroup>
  <!-- Include native library in publish output -->
  <NativeLibrary Include="libs/libcustom.so" />
</ItemGroup>

Size Optimization

Binary Size Reduction Options

<PropertyGroup>
  <PublishAot>true</PublishAot>

  <!-- Strip debug symbols (significant size reduction) -->
  <StripSymbols>true</StripSymbols>

  <!-- Optimize for size over speed -->
  <OptimizationPreference>Size</OptimizationPreference>

  <!-- Enable invariant globalization (removes ICU data) -->
  <InvariantGlobalization>true</InvariantGlobalization>

  <!-- Remove stack trace strings (reduces size, harder debugging) -->
  <StackTraceSupport>false</StackTraceSupport>

  <!-- Remove EventSource/EventPipe (if not using diagnostics) -->
  <EventSourceSupport>false</EventSourceSupport>
</PropertyGroup>

Typical Binary Sizes

Size Analysis

# Analyze what contributes to binary size
dotnet publish -c Release -r linux-x64 /p:PublishAot=true

# Use sizoscope (community tool) for detailed size analysis
# https://github.com/AdrianEddy/sizoscope

Self-Contained Deployment with runtime-deps

Native AOT produces self-contained binaries that include the .NET runtime. Use the runtime-deps base image for minimal container size since the runtime is already embedded in the binary.

# Build stage
FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
WORKDIR /src
COPY . .
RUN dotnet publish -c Release -r linux-x64 -o /app/publish

# Runtime stage -- use runtime-deps, not aspnet or runtime
FROM mcr.microsoft.com/dotnet/runtime-deps:10.0-noble-chiseled AS runtime
WORKDIR /app
COPY --from=build /app/publish .
ENTRYPOINT ["./MyApp"]

The runtime-deps image contains only OS-level dependencies (libc, OpenSSL, etc.) -- no .NET runtime. This is the smallest possible base image for AOT-published apps (~30 MB). See [skill:dotnet-containers] for full container patterns.

ASP.NET Core Native AOT

Minimal API Support (.NET 8+)

ASP.NET Core Minimal APIs support Native AOT. MVC controllers are not AOT-compatible (they rely on reflection for model binding, filters, and routing).

var builder = WebApplication.CreateSlimBuilder(args);

// Use source-generated JSON context
builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonContext.Default);
});

var app = builder.Build();

app.MapGet("/api/products/{id}", (int id) =>
    Results.Ok(new Product(id, "Widget")));

app.Run();

[JsonSerializable(typeof(Product))]
internal partial class AppJsonContext : JsonSerializerContext { }

record Product(int Id, string Name);

CreateSlimBuilder vs CreateBuilder

Use CreateSlimBuilder for Native AOT applications. It excludes features that require runtime code generation.

.NET 10 ASP.NET Core AOT Improvements

.NET 10 brings improvements across the ASP.NET Core and runtime Native AOT stack. Target net10.0 to benefit automatically.

<PropertyGroup>
  <TargetFramework>net10.0</TargetFramework>
  <PublishAot>true</PublishAot>
</PropertyGroup>

Request Delegate Generator improvements: The source generator that creates request delegates for Minimal API endpoints handles more parameter binding scenarios in .NET 10, including additional TypedResults return types and complex binding patterns. This reduces the need for manual workarounds that were required in .NET 8/9 when the generator could not produce AOT-safe code for certain endpoint signatures.

Reduced linker warning surface: Many ASP.NET Core framework APIs that previously emitted trim/AOT warnings (IL2xxx/IL3xxx) have been annotated or refactored for AOT compatibility. Projects upgrading from .NET 9 to .NET 10 will see fewer false-positive linker warnings when publishing with PublishAot.

OpenAPI in the webapiaot template: The webapiaot project template now includes OpenAPI document generation via Microsoft.AspNetCore.OpenApi by default, so AOT-published APIs get auto-generated API documentation without additional setup.

Runtime NativeAOT code generation: The .NET 10 runtime improves AOT code generation for struct arguments, enhances loop inversion optimizations, and improves method devirtualization -- resulting in better throughput for AOT-published applications without code changes.

Blazor Server and SignalR: Blazor Server and SignalR remain not supported with Native AOT in .NET 10. Blazor WebAssembly AOT (client-side compilation) is a separate concern covered by [skill:dotnet-aot-wasm]. For Blazor Server apps, continue using JIT deployment.

Compatibility snapshot (.NET 10):

Agent Gotchas

1. Do not use PublishAot in library projects. Libraries use IsAotCompatible (which auto-enables the AOT analyzer). PublishAot is for applications that produce standalone executables.
2. Do not use legacy RD.xml for type preservation. RD.xml is a .NET Native/UWP format that is silently ignored by modern .NET AOT. Use ILLink descriptor XML files and [DynamicDependency] attributes instead.
3. Do not use [DllImport] in new AOT code. Use [LibraryImport] (.NET 7+) which generates marshalling at compile time. [DllImport] may require runtime marshalling that is not available in AOT.
4. Do not use WebApplication.CreateBuilder() for AOT APIs. Use CreateSlimBuilder() which excludes reflection-heavy features. CreateBuilder() includes MVC infrastructure that is not AOT-compatible.
5. Do not use dotnet publish --no-actual-publish for analysis. That flag does not exist. Use dotnet build /p:EnableAotAnalyzer=true /p:EnableTrimAnalyzer=true to get diagnostic warnings without publishing.
6. Do not assume MVC controllers work with Native AOT. MVC relies on reflection for model binding, action filters, and routing. Use Minimal APIs for AOT-published web applications.

References

• Native AOT deployment
• ASP.NET Core Native AOT
• ILLink descriptor format
• LibraryImport source generation
• Optimize AOT deployments