access数据库访问错误,急!!!

以下是程序源码
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.OleDb;
namespace newryb
{
public partial class _Default : System.Web.UI.Page
{
      static string OleConn = ConfigurationSettings.AppSettings["ConnString"];
      protected void Page_Load(object sender, EventArgs e)
      {
         //Label1.Text = OleConn.ToString();
         init_bind();

      }
            public static bool  init_bind()
            {
               OleDbConnection con=new OleDbConnection(OleConn);
                  con.Open();
         OleDbCommand cmd=new OleDbCommand("select title,regdata from Tbl_News",con);
                  cmd.CommandType = CommandType.Text;
         OleDbDataReader rd=cmd.ExecuteReader();
                  if(rd.Read())
                  {
                     return true;
                  }
                  else
                  {
                     return false;
   }

            }
}
}
以下是web.config文件中access数据库的设置:
<appSettings>
   <add key="ConnString" value="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\inetpub\wwwroot\newryb\news.mdb"/>
</appSettings>
提示出错:
运行的时候出现错误,"异常详细信息: System.Data.OleDb.OleDbException: 至少一个参数没有被指定值
错误行:OleDbDataReader rd=cmd.ExecuteReader();
请各位高手帮忙解决一下.