IObjectSet<TEntity>.Attach Method (TEntity)
Notifies the set that an object that represents an existing entity must be added to the set.
Assembly: System.Data.Entity (in System.Data.Entity.dll)
Changes to the set may not be visible in an enumeration of the set until changes to that set have been persisted in some manner. This behavior depends on the specific implementation of the T: System.Data.Objects.IObjectSet`1.
Available since 4.0