First of all, the SQL looks OK. Does it work from the CLP?
It looks like your quotes are wrong on the SQL string. It looks like you have a double quote (") at the front, and a single (') at the end (this maybe just a typo).
I noticed that you are using ExecuteQuery to perform the operation. ExecuteQuery is only for SELECT statements since it returns a result set. Use ExecuteUpdate for all non-SELECT statements, including DDL statements.
Andy