The types of positional and named parameters for an attribute class are limited to the attribute parameter types, which are:

• One of the following types: bool, byte, char, double, float, int, long, short, string.
• The type object.
• The type System.Type.
• An enum type, provided it has public accessibility and the types in which it is nested (if any) also have public accessibility (Section 17.2).
• Single-dimensional arrays of the above types.