同一个程序运行不同的表时，update出错

Question

                string sCName = textBox3.Text;
                string SCIntro = textBox4.Text;
                string tm = DateTime.Now.ToString();
                string connString = ConfigurationManager.ConnectionStrings["connAccess1"].ConnectionString;
                using (OleDbConnection myconn = new OleDbConnection(connString))
                {
                    
                        myconn.Open();
                        string strSql = "select * from express order by id desc";
                            OleDbDataAdapter myDataAdapter = new OleDbDataAdapter(strSql, myconn);
                                                        OleDbCommandBuilder myCb = new OleDbCommandBuilder(myDataAdapter);
                            
                            DataSet myDataSet = new DataSet();
                            myDataAdapter.Fill(myDataSet, "express");
                            myDataAdapter.FillSchema(myDataSet, SchemaType.Source, "express");
                            DataTable myDataTable4 = myDataSet.Tables["express"];
                            //myCb.RefreshSchema();
                            DataRow myDataRow = myDataTable4.NewRow();
                            myDataRow["称编号"] = sPid;
                            //myDataRow["adr"] = sCName;
                            //myDataRow["tax"] = SCIntro;
                            //myDataRow["tim"] = tm;
                            myDataTable4.Rows.Add(myDataRow);
                                                        //myDataSet.AcceptChanges();
                            myDataAdapter.Update(myDataSet, "express");///运行到这里出错**代码是这样的，表“list”和表“express”是同一个数据库下的两个表格，但是当我把上面的express全换成list 运行没有错误，而当express时 程序运行到**会出错，请问是哪里错误了