ds = new System.Data.DataSet();
            ds = dsFromMainForm;
            
            row = ds.Tables[0].Select(
                                       "entMCode = '" + entMCode + "' AND " +
                                       "toCode = 'FINSTRU' AND " +
                                       "toNode = '" + toNode + "'");
            
            InitializeComponent();

            // добавим данные в поля
            textBox2.Text = row[2].ToString();

textBox2.Text = row[2].ToString();

private DataRow[] row;

  textBox2.Text = row[0].ItemArray[2].ToString();