Excel okuma Datasete atma

string Platform = "";
OpenFileDialog ac = new OpenFileDialog();   
     ac.Filter = "Excel dosyaları(*.xlsx)|*.xlsx"; Platform = "x64. Sadece XLSX Dosyaları";
        ac.Title = "Platform " + Platform;
        ac.ShowDialog();
        string ExcelYol = ac.FileName.ToString();

        DataTable dtexcel = new DataTable();

        if (ExcelYol.Trim().Length > 0)
        {
            DataTable schemaTable = new DataTable();
            string strConn = "";
            DataSet ds = new DataSet();
            strConn = "Provider = Microsoft.ACE.OLEDB.12.0; Data Source=" + ExcelYol + "; Extended Properties = \"Excel 12.0; HDR = Yes; IMEX = 0\"";
            OleDbConnection conn = new OleDbConnection(strConn);
            conn.Open();
            schemaTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
            DataRow schemaRow = schemaTable.Rows[0];
            string sheet = schemaRow["TABLE_NAME"].ToString();
            if (!sheet.EndsWith("_"))
            {
                string query = "SELECT  * FROM [" + sheet + "]";
                OleDbDataAdapter daexcel = new OleDbDataAdapter(query, conn);
                dtexcel.Locale = CultureInfo.CurrentCulture;
                // daexcel.Fill(dtexcel);
                daexcel.Fill(ds, "ExcelOkunan");
            }
            conn.Close();

            SplashScreenManager.ShowForm(typeof(Bekleyiniz));
            int eklenen = 0;
            int guncellenen = 0;

            for (int ii = 0; ii < ds.Tables["ExcelOkunan"].Rows.Count; ii++)
            {
                // string LOGICALREF = ds.Tables["ExcelOkunan"].Rows[ii][0].ToString();
                // string MARKA = ds.Tables["ExcelOkunan"].Rows[ii][1].ToString();
                string CODE = ds.Tables["ExcelOkunan"].Rows[ii][2].ToString();
                string NAME = ds.Tables["ExcelOkunan"].Rows[ii][4].ToString();
                string GRUPKODU = ds.Tables["ExcelOkunan"].Rows[ii][5].ToString();