public void Seed(DbContext dbContext) { var address = new Address { Street = "Musterweg", Number = "1A", Zip = "12345", City = "Musterstadt" }; dbContext.Set <Address>().Add(address); var building = new Building { Name = "neuer Name" }; dbContext.Set <Building>().Add(building); var room1 = new BuildingRoom { Name = "102", Area = 100, Height = 220, Description = null, Building = building }; var room2 = new BuildingRoom { Name = "103", Area = 20, Height = 220, Building = building }; dbContext.Set <BuildingRoom>().Add(room1); dbContext.Set <BuildingRoom>().Add(room2); dbContext.SaveChanges(); }