String sql = "INSERT INTO News ( Category,Matter,Subject,date ) VALUES (@Category,@Matter,@Subject,@date)";
SqlCommand cmd = new SqlCommand(sql, con);
cmd.Parameters.Add("@Subject", SqlDbType.VarChar, 100).Value = txtsub.Text;
cmd.Parameters.Add("@Matter", SqlDbType.VarChar, 8192).Value = txtnews.Text;
cmd.Parameters.AddWithValue("@Category", dropdwncate.SelectedValue);