This method must be called after modifying, installing or uninstalling add-ins. When calling Update, every add-in added to the registry is parsed and validated, and if there is any error it will be rejected. It will also cache add-in information needed at run-time. If during the update operation the registry finds new add-ins or detects that some add-ins have been deleted, the loaded extension points will be updated to include or exclude extension nodes from those add-ins.