更改column时有可能遇到问题。貌似权限问题：
saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created. you have either made changes to a table that can't be re-created or enabled the option prevent saving changes that require the table to be re-created.
执行类似语句可以解决：
alter table ImportUserData alter column SolutionName nvarchar(500)
转载于:https://www.cnblogs.com/Fly-sky/archive/2010/05/13/1734794.html
