[#\SqlParameter] Sintassi non corretta in prossimità di '?'.

                    using (SqlConnection conn2 = new SqlConnection(MainForm.Database()))
                    {

                        conn2.Open();
                        query = "SELECT COUNT(id) FROM categoria WHERE id=?";
                        SqlCommand oleCmd2 = new SqlCommand(query, conn2);

                        prm = new SqlParameter();
                        prm.Direction = ParameterDirection.Input;
                        prm.DbType = DbType.String;
                        prm.Value = reader["categoria"].ToString();
                        oleCmd2.Parameters.Add(prm);

                        cat = (int)oleCmd2.ExecuteScalar();
                        conn2.Close();
                    }

using (SqlConnection conn2 = new SqlConnection(MainForm.Database()))
                    {

                        conn2.Open();
                        query = "SELECT COUNT(id) FROM categoria WHERE id=@id";
                        SqlCommand oleCmd2 = new SqlCommand(query, conn2);

                        prm = new SqlParameter();
                        prm.Direction = ParameterDirection.Input;
                        prm.DbType = DbType.String;
                        prm.Name = "@id";
                        prm.Value = reader["categoria"].ToString();
                        oleCmd2.Parameters.Add(prm);

                        cat = (int)oleCmd2.ExecuteScalar();
                        conn2.Close();
                    }