vs2005 连接ACCESS代码

         string username = Request["username"].ToString();
        string password = Request["password"].ToString();

        string DBPath = Server.MapPath("testdb.mdb");
        OleDbConnection dbcon = new OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source=" + DBPath + "");
        dbcon.Open();

        OleDbCommand ocmd = new OleDbCommand("select count(*) from login where username='+username+' and password='+password+'", dbcon);
        int count = Convert.ToInt32(ocmd.ExecuteScalar());

        if (count < 0)
        {
            Response.Redirect("main.aspx");
        }
        else
        {
            Response.Write("error");
        }

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