[Breaking change]: Replace DAMT.All with more restricted annotation on InvokeMember/FindMembers/DeclaredMembers

[agocke]

[Breaking change]: Replace DAMT.All with more restricted annotation on InvokeMember/FindMembers/DeclaredMembers

Description

Starting in .NET 10.0, the System.Reflection APIs InvokeMember, FindMembers, and DeclaredMembers have been updated to use more restricted annotations instead of DAMT.All. This change affects scenarios where developers implement the IReflect interface or derive from System.TypeInfo. The previous use of DAMT.All was overly permissive and could lead to unintended behavior, such as capturing interface methods implemented by a class or generating warnings due to unsafe reflection calls.

This change improves the accuracy of annotations and ensures better compatibility with trimming and reflection scenarios. However, it introduces a breaking change for developers who have implemented IReflect or derived from System.TypeInfo, as they may need to update their annotations to align with the new behavior.

Version

.NET 10.0

Previous behavior

The InvokeMember, FindMembers, and DeclaredMembers APIs used the DAMT.All annotation, which was overly permissive. This could result in capturing additional members, such as interface methods implemented by a class, and potentially cause runtime warnings or unsafe reflection calls.

New behavior

The InvokeMember, FindMembers, and DeclaredMembers APIs now use more restricted annotations, which provide better control over the members captured during reflection. Developers implementing IReflect or deriving from System.TypeInfo must update their annotations to match the new behavior.

Ex:

class MyType : IReflect
{
[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.NonPublicFields |
            DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods |
            DynamicallyAccessedMemberTypes.PublicProperties | DynamicallyAccessedMemberTypes.NonPublicProperties |
            DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
        public object InvokeMember(string name, BindingFlags invokeAttr, Binder? binder, object? target,
            object?[]? args, ParameterModifier[]? modifiers, CultureInfo? culture, string[]? namedParameters)
        { }
}

Type of breaking change

• Source incompatible: When recompiled using .NET 10.0 or targeting the new runtime, existing source code may require changes to annotations to compile successfully.
• Behavioral change: Existing binaries might behave differently at runtime due to the updated annotations.

Reason for change

The change was introduced to improve the accuracy of annotations in System.Reflection APIs and to address issues caused by the overly permissive DAMT.All annotation. This ensures better compatibility with trimming and reflection scenarios, reduces runtime warnings, and prevents unsafe reflection calls.

Recommended action

Developers who implement IReflect or derive from System.TypeInfo should review their code and update annotations to align with the new behavior. Specifically:

1. Replace DAMT.All annotations with more restricted annotations, such as DynamicallyAccessedMemberTypes.PublicMethods, DynamicallyAccessedMemberTypes.NonPublicMethods, or other appropriate types.
2. Test reflection scenarios to ensure that the updated annotations capture the intended members and do not introduce runtime errors or warnings.

Feature area

• Core .NET libraries
• System.Reflection

Affected APIs

• System.Reflection.IReflect.InvokeMember
• System.Reflection.IReflect.FindMembers
• System.Reflection.TypeInfo.DeclaredMembers

Additional resources

For more information on DynamicallyAccessedMembers annotations and their usage, refer to the Microsoft documentation on trimming and reflection.

---

Associated WorkItem - 495864