Restricting permission to drop column in SQL Server?

Question

ALTER TABLE [dbo].[Client] ADD [Awesomness] [nvarchar](max)
ALTER TABLE [dbo].[Client] DROP COLUMN [Awesomness]

The second command I don't want to be successful, I don't want any DROP COLUMN to succeed. So I created a user for my database, just wondering how I can deny this user the permission to DROP COLUMN . I set up a trigger but that doesn't seem to take care of DROP COLUMN . Is there anyway I could restrict this?

CREATE TRIGGER [TR_DB_NO_DROPPING_OBJECTS_2]
on DATABASE
FOR 
DROP_PROCEDURE,DROP_FUNCTION,DROP_VIEW,DROP_TABLE, DROP_DEFAULT,DROP_EXTENDED_PROPERTY
AS
 BEGIN
    IF  --only two accounts allowed to drop stuff
   suser_name() NOT IN('test' )

 BEGIN
 --raise an error, which goes to the error log
 RAISERROR('Unauthorized use of drop object from inpermissible host.', 16, 1)
 --prevent the drop
  ROLLBACK
    END
 --if it got to here, it was the "right" user from the "right" machine (i hope)
 END

The roles I've assigned my user.

use Hasan
go
EXEC sp_addrolemember N'db_datareader', N'TestUser'
go

use Hasan
go
EXEC sp_addrolemember N'db_datawriter', N'TestUser'
go

use Hasan
GO
GRANT EXECUTE TO [TestUser]
GO

use Hasan
GO
GRANT INSERT TO [TestUser]
GO

use Hasan
GO
GRANT SELECT TO [TestUser]
GO

use Hasan
GRANT ALTER TO [TestUser]
GO

use Hasan
GO
GRANT UPDATE TO [TestUser]
GO

use Hasan
GO
GRANT DELETE TO [TestUser]
GO

Answer 1

That would be an Alter_Table DDL event. See if that works for you.

Also, I am not sure if you have looked into roles. Granting dbwriter and dbreader allows CRUD operations but no changes to DDL.

https://msdn.microsoft.com/en-us/library/ms189121.aspx

EDIT: This example does not check for a user but it works on my test table:

CREATE TRIGGER testtrig 
ON Database 
FOR alter_table 
AS 
    Declare @Msg nvarchar(max) = (SELECT EVENTDATA().value('(/EVENT_INSTANCE/TSQLCommand/CommandText)[1]','nvarchar(max)'))
     If @Msg Like '%Drop Column ColumnA%'
     Rollback
GO

There is probably a better way than parsing the message text like in my example, this was just a quick test.

Also remember this is just a safety to let the user know they should not drop this column. If they have DDL rights they can disable or delete the trigger.