Is .Net attribute feature used at compile-time or run-time or both?

Question

In .Net, is the attribute feature used at compile-time or run-time or both? Can you give me some examples?

Answer 1

Attributes are output as metadata to the assembly at compile time. This meta data is then used at runtime via reflection - for example using GetCustomAttributes().

Some attributes are used by the compiler at compile time, too. For example the compiler looks at the AttributeUsageAttribute to determine if an attribute can be used for a specific object.