your create table name as update, its a keyword, so use your table name like this [update] it wont show error
Follow the below code:
"
string ins = "insert into [update] (Regid,Rollno,Name,Course,Noofbooks,Bookid,Bookname) Values(@Regid,@Rollno,@Name,@Course,@Noofbooks,@Bookid,@Bookname)";