In the current version, the array always contains a single object. It can be either an int or Guid value depending on which one is actually used for binding this data. For example, if you bind AppointmentStorage to the database and set IndexMapping, this property will return an int value. If you set IdMapping, this property will return a Guid value.

In future versions working with compound keys might be implemented. In such case this property will return array of objects composing the key.