Question

Just curious, see MemberInfo.GetCustomAttributes. Is it hinting that it may contain a non-Attribute object?

Answer 1

This is because the CLI specification doesn’t enforce that attributes derive from Attribute.

The specification, in II Part 21 (page 225), states:

While
any user-defined type can be used as an attribute, CLS compliance requires that attributes will be instances of
types whose base class is System.Attribute. The CLI predefines some attribute types and uses them to control
runtime behavior. Some languages predefine attribute types to represent language features not directly
represented in the CTS. Users or other tools are welcome to define and use additional attribute types.

Basically, the CLR itself can’t make a guarantee that the result will be Attribute – this is only true in CLS compliant languages. Non-CLS compliant languages are allowed to have attributes of any type, whic means ICustomAttributeProvider.GetCustomAttributes (which is the implemented interface in question) needs to provide a mechanism to get non-Attribute derived attributes.