高手看看为什么老是出现这样的错误？

下面我把源码贴出来，在DB.aspx.cs的源码是这样的：
public class DB
{
    public static OleDbConnection Getconn()
    {
        OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data source=" + System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["ConnectionString"].ToString()));
        if (conn.State.Equals(ConnectionState.Closed))
        {
           conn.Open();
        }
        return conn;
        }
        private static void closeConnection()
    {
        OleDbConnection conn = DB.Getconn();
        OleDbCommand cmd = new OleDbCommand();
        if (conn.State == ConnectionState.Open)
        {
            conn.Close();
            conn.Dispose();
            cmd.Dispose();
        }
    }
public static void binddatalist(string sql, DataList dl)
    {
        try
        {
            OleDbConnection conn = DB.Getconn();
            DataSet ds = getdataset(sql);
            dl.DataSource = ds.Tables[0].DefaultView;
            dl.DataBind();
        }
        catch (Exception e)
        {
            throw new Exception(e.Message);

        }
        finally
        {
            closeConnection();
        }
    }
}
然后在网页的后台引用如下：
string topsql1 = "select top 10 * from info  order by hits,id desc";//教育动态
        DB.binddatalist(topsql1, this.DataList1);
时而可以运行，时而出现上面所说的情况。为什么？怎么解决？谢谢！！