NPersistence Reference Guide
The MapKey type exposes the following fields.
XNA Framework Only
.NET Compact Framework Only
(Optional) The name of the persistent field or property of the associated entity that is used as the map key. Default: If the name element is not specified, the primary key of the associated entity is used as the map key. If the primary key is a composite primary key and is mapped as IdClass, an instance of the primary key class is used as the key.