I have a class hierarchy that I want to map across several tables using Entity Framework 4.1 Code First. It\'s like table-per-type (TPT) but I also want a discrimator column
Unfortunately this is not supported. Discriminator column can be used only in TPH. TPT differs entity types by mapped tables and it always produces those terrible queries. It could be nice feature so perhaps suggestion on Data UserVoice would make it implemented one day.
Update
There is already a suggestion on user voice for this titled "Discriminator column support in TPT inheritance".