When I create it in SQLServer Management Studio, and import the database in DDT, I can't see that it is a computed column.
Thanks for that explanation. I do understand what you are talking about, but SQL columns with Computed formulas are not currently supported with the DDT, regardless of whether or not the values for those columns are persisted. As Trent mentioned, utilizing a custom property on the BO and handling the computation either within the BO, or in the query (be it an in-line query, a SPROC, or a CLR SPROC) is the supported method to accomplish that type of functionality.
As far as adding the computed column as a future enhancement, we will of course look at adding that functionality, but it will not be in the near future. We are currently populating those column lists using SMO, which doesn't return the necessary information to interpret computed columns. As such, we won't be able to look at adding this until we do a low-level re-write of the DDT.
Thanks,
Dustin