Get By Distinguished Name
This is the fastest method to retrieve an entry when you know the distinguished name. This is done by performing a query with a base search scope. There's a method for mapped objects and IDirectoryAttributes.
string dn = "CN=Test User,CN=Users,DC=example,DC=com";
User user = context.GetByDN<User>(dn);
IDirectoryAttributes attributes = context.GetByDN(dn);