how to print barcode labels in c# Troubleshooting in Visual C#.NET

Encoding Denso QR Bar Code in Visual C#.NET Troubleshooting

Page containing HTML form and Database Results component returns an error when first displayed If you create a Database Results component that receives criteria from an HTML form on the same Web page, displaying the page might return a message such as the following:

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Database results error The operation failed. If this continues, please contact your server administrator.

Older versions of the component might display a message like this:

Database Results Error Description: [Microsoft][ODBC Microsoft Access Driver] Extra ) in query expression '(CategoryID =)'. Number: -2147217900 (0x80040E14) Source: Microsoft OLE DB Provider for ODBC Drivers One or more form fields were empty. You should provide default values for all form fields that are used in the query.

Such messages occur because the database query in a Database Results component runs every time a visitor requests the Web page including the first time, before the Web visitor has entered any query fields. With missing criteria values, the database query fails. To avoid this problem, do either of the following: Put the HTML form and the Database Results region on different pages. Use the Defaults dialog box (shown on the left in Figure 36-20) to assign defaults for all input fields used in the query. Assigning default values to the forms field has no effect. The browser fills in form field defaults after receiving the Web page, which is after the reported error occurs.

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Figure 36-24. The Database Results component populated the drop-down list in this Web page with values from a database.

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Database Results drop-down lists don t preserve selections When a Database Results drop-down list appears in a form that, as shown in Figure 36-16, uses the same Web page for input and output, visitors who select a value, click Submit, and receive a new version of the page expect their selection to remain in effect. In fact, a Database Results drop-down list always positions the list at the first entry. This limits the usefulness of Database Results drop-down lists.

To learn how to create a database-driven drop-down box that retains its value, refer to Recycling Form Element Values, in Appendix J.

The objects displayed as <<CategoryID>>, <<ProductID>>, <<ProductName>>, <<SupplierID>>, and so forth in Figure 36-22 are Database Column Value components. These components are valid only inside the ASP version of a Database Results region, and each one contains the name of a database field to display. Whenever the Database Results region has a record to display, it replaces each Database Column Value component with the value of its corresponding field. Because Database Column Value components exist only within the ASP version of a Database Results region, you can t use the techniques in this section to modify an ASP.NET version of a Database Results region. Instead, you must modify the ASP.NET DataGrid control that the Database Results Wizard creates. To do this in FrontPage requires working in Code view and therefore requires intimate knowledge of the DataGrid control.

For more information about the ASP.NET DataGrid control, browse msdn.microsoft.com and search for the terms framework, DataGrid, and class.

Here are the steps to insert a new Database Column Value component:

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Figure 36-25. This dialog box configures the database field that a Database Column Value component will display.

Use the options in this dialog box as follows:

To specify or modify the database field you want to display, select the field you want from the drop-down list.

Select this check box if the database field you specified contains HTML that you want the browser to display. This choice is appropriate if, for example, the field contains the HTML to display a hyperlink or a picture.

Normally, the Database Results component translates HTML characters such as < and > to symbolic equivalents like < and >. This keeps the browser from misX interpreting these characters when they appear in normal text in a description field, for example. However, it interferes with display of HTML you ve purposely included in the query results. Selecting this option turns off the translation.