请问：数据库插入数据的有关问题

请教：数据库插入数据的问题
现在做的是Windows mobile 6.0 移动应用程序开发
[code=C#][/code]
private SqlCeConnection conn = null;
  private SqlCeCommand sqlCom;
  private SqlCeDataReader myReader;

  //==========================================================================
  //连接数据库：
  public void PPCSQL()
  {
  string apppath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.FullyQualifiedName);//取得当前程序目录
  apppath += "\\AppDatabase2.sdf";
  try
  {
  conn = new SqlCeConnection("Data Source=" + apppath);
  sqlCom = new SqlCeCommand();
  sqlCom.Connection = conn;

  // conn.Open();

  // int nun = sqlCom.ExecuteNonQuery();
  /*
  if (nun >0)
  {
  MessageBox.Show("插入成功 ");

  }*/
  // conn.Close();
  }
  catch (Exception ex)
  {
  MessageBox.Show("PPCSQL()\r\n" + ex.Message);
  }
  }

  //==========================================================================
  //操作前先打开数据库：
  public bool Open()
  {
  bool res = false;
  try
  {
  if (conn.State == System.Data.ConnectionState.Broken)
  {
  conn.Close();
  }
  conn.Open();
  res = conn.State == System.Data.ConnectionState.Open;
  }
  catch (Exception ex)
  {
  MessageBox.Show("Open()\r\n" + ex.Message);
  conn.Close();
  }

  return res;
  }
  //==========================================================================
 //插入新记录:
  // public void insterOneItem(object_HaoMaObj Qi)
  public void insterOneItem()
  {
  // string sql = "insert into shuju(menu_id,menu_name,c,d,e,f,u,a,b) values(" + Qi.Menu_id.ToString() + "," + Qi.Menu_name.ToString() + "," + Qi.C.ToString() + "," + Qi.D.ToString() + "," + Qi.E.ToString() + "," + Qi.F.ToString() + "," + Qi.U.ToString() + "," + Qi.A.ToString() + "," + Qi.B.ToString() + ")";
  // string sql = "insert into shuju(menu_id,menu_name,c,d,e,f,u,a,b) values(@menu_id,@menuname,@c,@d,@e,@f,@u,@a,@b)";
  string sql = "insert into shuju(menu_id,menu_name,c,d,e,f,u,a,b) values(" + 1 + "," + 1 + "," + 1 + "," + 1 + "," + 1 + "," + 1 + "," + 1 + "," + 1 + "," + 1 + ")";
  try
  {
   
   
  sqlCom.CommandText = sql;
   
  //sqlCom =new SqlCeCommand(sql ,conn );
  //sqlCom.Connection = conn;
  /*
  sqlCom.Parameters.Add("@menu_id", SqlDbType.Int);
  sqlCom.Parameters["@menu_id"].Value = Qi.Menu_id;
  sqlCom.Parameters.Add("@menuname", SqlDbType.Int);