How does SelectByKey work in the Repository Pattern?

Question

Hi,

I'm implementing the repository pattern found here Implementing Repository Pattern With Entity Framework

One of the methods he has is SelectByKey. In the comment called Key field impementation by [email protected], there was a suggestion to make it a little more generic of an implementation:

I would like to add a simple mechanism to identify the Key field of an entity type when it's name is not ID in the generic repository implementation to make it a little more generic:

First he lists the actual implementation, then he lists the implementation he suggests. Please read the comment for details on his implementation.

Can anyone tell me how exactly this works -- How would a method in my service layer call SelectByKey?