PowerDesigner provides full support for C# 2.0 custom attributes, which allow you to add metadata to your code. This metadata can be accessed by post-processing tools or at run-time to vary the behavior of the system.
You can use built-in custom attributes, such as System.Attribute and System.ObsoleteAttribute, and also create your own custom attributes to apply to your types.
For general information about modeling this form of metadata in PowerDesigner, see Annotations (OOM).