当 DataGrid 行选择为空白时，ComboBox 输入字符串格式异常

Question

我有一个从 SQL Server 数据库填充的DataGrid，我有一个鼠标双击事件，它打开一个新窗口并填充Textboxes 和ComboBoxes。

我有一个小问题。如果所选行的名为“RTTYPE”的列是空白的，我将得到一个System.FormatException: Input string was not in a correct format，然后ComboBox 显示列表中的第一个值项。

如果所选行为空白，我希望 ComboBox 保持空白。请帮忙！

        private void dtGrid_MouseDoubleClick(object sender, MouseButtonEventArgs e)
    {

        // User double clicks on DataGrid Row
        // Open new Window
        // Populate selected textboxes with selected datarow
        DataGrid gd = (DataGrid)sender;
        DataRowView row_selected = gd.SelectedItem as DataRowView;

        var windowToOpen = new Window1();

        if (gd != null)
        {
            // Textboxes
            windowToOpen.txt_RowRecrd.Text = row_selected["DSP_ID"].ToString();
            windowToOpen.txt_acctnumber.Text = row_selected["ACCOUNT"].ToString();
            windowToOpen.txt_analyst.Text = row_selected["TX_EMPLOYEE"].ToString();
            windowToOpen.txt_custname.Text = row_selected["CUST_NAME"].ToString();
            windowToOpen.txt_address.Text = row_selected["PREM_ADDR"].ToString();
            windowToOpen.txt_Status.Text = row_selected["Status"].ToString();
            windowToOpen.txt_opened.Text = row_selected["OPENED"].ToString();
            windowToOpen.txt_deadline.Text = row_selected["DEADLINE"].ToString();
            windowToOpen.txt_DaysOpen.Text = row_selected["DaysOpen"].ToString();
            windowToOpen.txt_DateResolved.Text = row_selected["DATERSLVD"].ToString();
            windowToOpen.txt_revcls.Text = row_selected["RateType"].ToString();
            windowToOpen.txt_WFMissuedBy.Text = row_selected["NM_USER"].ToString();
            windowToOpen.txt_firstreview.Text = row_selected["FR_DT_FIRSTREV"].ToString();
            windowToOpen.txt_Latestupdate.Text = row_selected["FR_TS_LATESTUPD"].ToString();
            windowToOpen.txt_reviewNotes.Text = row_selected["FR_CMMNT"].ToString();
            windowToOpen.txt_ResolutionNotes.Text = row_selected["COMMENT"].ToString();


            // ComboBoxes
            SqlConnection connection = new SqlConnection("Data Source=WINDOWS-B1AT5HC\\SQLEXPRESS;Initial Catalog=CustomerRelations;Integrated Security=True;");

            try
            {
                SqlDataAdapter Status_data = new SqlDataAdapter("SELECT RPTID, ReportType FROM [hb_RptType]", connection);
                DataSet ds = new DataSet();
                Status_data.Fill(ds, "t");

                windowToOpen.cmb_UtilityRptTyp.ItemsSource = ds.Tables["t"].DefaultView;
                windowToOpen.cmb_UtilityRptTyp.DisplayMemberPath = "ReportType";
                windowToOpen.cmb_UtilityRptTyp.SelectedValuePath = "RPTID";
                windowToOpen.cmb_UtilityRptTyp.SelectedValue = row_selected["RPTTYPE"].ToString();

                // windowToOpen.cmb_UtilityRptTyp.SelectedIndex = 3; //  Convert.ToInt32( row_selected["RPTTYPE"].ToString());
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }

            windowToOpen.Show();
        }
        else
        {
            return;
        }

    }

Answer 1

如果您为Selected Value 或ComboBox 选择null，则会引发异常。如果您的数据只是一个纯字符串，您可以使用SelectedItem 而不是SelectedValue。或者执行空检查：

if(row_selected["RPTTYPE"] is string rateType) windowToOpen.cmb_UtilityRptTyp.SelectedValue = rateType;
else UtilityRptTyp.SelectedIndex = -1;