use EnVisage
if exists(select 1 from sys.columns where Name = N'PagePreferences' and Object_ID = Object_ID(N'AspNetUsers'))
	set noexec on
begin transaction
		ALTER TABLE [dbo].[AspNetUsers] ADD [PagePreferences] [nvarchar](max) NULL
		go
		UPDATE [dbo].[AspNetUsers] SET [PagePreferences]='' WHERE [PagePreferences] IS NULL
		go
		ALTER TABLE [dbo].[AspNetUsers] ALTER COLUMN [PagePreferences] [nvarchar](max) NOT NULL

commit transaction