Compelling Reasons to Use Marker Interfaces Instead of Attributes

I generally avoid “marker interfaces” because they don’t allow you to unmark a derived type. But that aside, here are some of the specific cases that I have seen where marker interfaces would be preferable to built-in meta-data support:

1. Run-time performance sensitive situations.
2. Compatibility with languages that don’t support annotation or attributes.
3. Any context where the interested code may not have access to the metadata.
4. Support for generic constraints and generic variance (typically of collections).