This type parameter is covariant. That is, you can use either the type you specified or any type that is more derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
The ITagger<T> type exposes the following members.
For more information about tagging, see the "Tags and Classifiers" section of Inside the Editor. For information about extending and adding tags, see the "Extending Tags" section of Editor Extension Points.