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DISP003: Reflection Without AOT Annotation

PropertyValue
Diagnostic IDDISP003
TitleReflection usage without AOT annotation
CategoryExcalibur.Dispatch.Compatibility
SeverityWarning
Enabled by defaultYes

Cause​

A method uses reflection-based operations (such as Type.GetType(), Activator.CreateInstance(), or Assembly.GetTypes()) without proper AOT annotations. This may cause issues when the application is published as Native AOT.

Example​

The following code triggers DISP003:

// Warning DISP003: Method 'ResolveHandler' uses 'Activator.CreateInstance'
// without AOT annotation
public class HandlerFactory
{
    public object ResolveHandler(Type handlerType)
    {
        return Activator.CreateInstance(handlerType)!;
    }
}

How to Fix​

Option 1: Add AOT annotations to inform the trimmer:

using System.Diagnostics.CodeAnalysis;

public class HandlerFactory
{
    [RequiresDynamicCode("Creates handler instances dynamically")]
    public object ResolveHandler(
        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]
        Type handlerType)
    {
        return Activator.CreateInstance(handlerType)!;
    }
}

Option 2 (Recommended): Use source generators instead of reflection:

// Source generators resolve handlers at compile time,
// avoiding reflection entirely
services.AddDispatch(typeof(Program).Assembly);

When to Suppress​

Suppress this warning if your application will never be published as Native AOT and you are comfortable with the reflection-based approach.

See Also​