总算找到了问题的原因了，爽，不过感觉自己太粗心了。

这段代码一直找不到什么地方错了，编译能通过，但是就是没有办法取得数据库中的值，十分郁闷。

到csdn上拜了个高手为师，结果都是指出了一些无关紧要的错误，不过还是得到了一些检查bug的基本方法。

最后在查网页信息的时候，对照人家写的连接Access的源代码一条一条看，才发现原来是红色部分出了问题，而且是两个问题：

1.provider的值给错了Microsoft.Jet.OleDb.4.0写成了Microsoft.Jet.Ole.4.0

2.Server.MapPath(("hqcs.mdb")取出的值居然是D:/hqcs/page/hqcs.mdb,而实际的路径是D:/hqcs/DataSource/hqcs.mdb,这个问题我现在还没找到原因，msdn上关于server.mappath()有好几个版本，我还不能确定到底应该使用那个版本。

namespace hqcs.ascx
{
 using System;
 using System.Data;
 using System.Drawing;
 using System.Web;
 using System.Web.UI.WebControls;
 using System.Web.UI.HtmlControls;

 //database
 using System.Data.OleDb;
 using System.Data.SqlClient;

 
 

 //Global funstions
 //using hqcs.Global;

 /// <summary>
 ///  Summary description for hqcsNavigationBar.
 /// </summary>
 public class dtgNavigationBar : System.Web.UI.UserControl
 {
  protected System.Web.UI.WebControls.DataGrid dtgNBar;
  protected System.Web.UI.WebControls.Label Label1;

  private OleDbConnection conNBar;
  private OleDbCommand cmdNBar;
  private OleDbDataAdapter dapNBar;
  private DataSet dstNBar;
  private DataView dtvNBar;

  private void Page_Load(object sender, System.EventArgs e)
  {
   // Put user code to initialize the page here
   //connect to database
   //string strConnAccess = "Provider = Microsoft.Jet.Ole.4.0;Data Source = " + Server.MapPath("hqcs.mdb");
   string strConnAccess = "Provider = Microsoft.Jet.OleDb.4.0;";
   strConnAccess += "Data Source = D://hqcs//DataSouce//hqcs.mdb";

   conNBar = new OleDbConnection();
   conNBar.ConnectionString = strConnAccess;
   try
   {
    conNBar.Open();

    //cmdNBar = new OleDbCommand("Select * from hqcs_NavigationBarItems",conNBar);
    cmdNBar = new OleDbCommand();
    cmdNBar.CommandText = "SELECT * FROM hqcs_NavigationBarItems";   
    cmdNBar.Connection = conNBar;
    

    dapNBar = new OleDbDataAdapter(cmdNBar);
    dstNBar = new DataSet();
    dapNBar.Fill(dstNBar,"NavigationBar");

    dtvNBar = dstNBar.Tables["NavigationBar"].DefaultView;

    int nRecords = 0;
    nRecords = dstNBar.Tables["NavigationBar"].Rows.Count;
    Label1.Text = nRecords.ToString();
    

    dtgNBar.DataSource = dtvNBar;
    dtgNBar.DataBind();

    conNBar.Close();
   }
   catch(Exception ex)
   {
    Console.WriteLine(ex.Message);
   }
   
  }

  #region Web Form Designer generated code
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: This call is required by the ASP.NET Web Form Designer.
   //
   InitializeComponent();
   base.OnInit(e);
  }
  
  /// <summary>
  ///  Required method for Designer support - do not modify
  ///  the contents of this method with the code editor.
  /// </summary>
  private void InitializeComponent()
  {
   //this.ID = "dtgNBar";
   this.Load += new System.EventHandler(this.Page_Load);

  }
  #endregion

  
 }
}

 

接下来我想对代码进行一些优化，把连接数据库的字段写到web.config中去。

在web.config中添加了以下代码：

<appSettings>

<!-- the connect to database-->
<!-- connect to Access database -->
<add key = "connAccess" value = "Provider = Microsoft.Jet.OleDb.4.0; Data Source =D:/hqcs/DataSouce/hqcs.mdb"></add>
<!--connect to mssql2000-->
<add key="conSql" value="server=Localhost;UID=sa;PWD=sa; database=hqcs;"></add>

</appSettings>

然后再代码中去除原来的字段，加入以下代码：

using System.Configuration;

..............

   /*
   string strConnAccess = "Provider = Microsoft.Jet.OleDb.4.0;";
   strConnAccess += @"Data Source = D:/hqcs/DataSouce/hqcs.mdb";
   */
   string strConnAccess = ConfigurationSettings.AppSettings["connAccess"];

用来获得连接数据库的string。