How do I add a RowVersion attribute to a EF4 class

Question

I am using EF4 and creating classes through the Entity design surface then generating the database from them. I want to add an attribute to some of the classes to show the timestamp they were last updated.

I have added a Version attribute to them, but I don't know which .Net datatype to associate with them so they become either Timestamp or RowVersion in the database when it is generated.

Any ideas?