FILE: How to Populate a List or Combo Box with Recordset Data

 Last reviewed: March 5, 1998
Article ID: Q182061
The information in this article applies to:
  • The Microsoft Foundation Classes (MFC)
  • Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 5.0sp1, 5.0sp2, 5.0sp3

SUMMARY

The DaoDDX.exe sample demonstrates how to populate list and combo boxes with a column from a CDaoRecordset. The information this sample supplies can be used to provide the same functionality for Crecordset based objects. This sample uses two DDX functions to provide data exchange between the recordsets and the list and combo boxes.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library: 

 ~ DaoDDX.exe (size: 610816 bytes)
For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base: 

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from Online Services
This sample contains two DDX functions DDX_BindTextFieldListBoxToColumn() and DDX_BindTextFieldComboBoxToColumn() to link a particular column from a recordset to a list or combo box. These functions take the following parameters:
  • A CDataExchange object
  • The resource ID of the control to bind to
  • The name of the column to bind to
  • A CDaoRecordset object to use to retrieve the information.

These functions also take the following two optional parameters (both of which default to false):
  • Whether or not to update the column when saving
  • Whether or not to allow repeated values in the control

When viewing records, these functions first save the current position in the recordset passed in. This position is treated as the current value of the current record, and is selected when the population is complete. Then the function iterates through all the records in the recordset, either adding the current value to the control, or rejecting the current value if it cannot be converted to a string or it is a duplicate value and duplicate values are not being accepted. The function finishes by restoring the original position of the recordset and then selecting that entry.

When saving, if the optional parameter to update the column is set, the function takes the current record, and updates the field in the column passed in with the currently selected item (or the modified text in a combo box situation). This method would be used in tables where the choices being given are not a foreign key. In the foreign key situation, which is the method used in the example, a second DDX function would be used to tie the selected value for that particular control to a field in the result set given.

The function CDaoDDXView::PositionRecordsets() moves through the foreign recordsets, positioning each on the record denoted by the key value in the CDaoDDXView::m_pEnrollmentSet object. This allows the proper item to be selected in each of the controls, because the selection is based on the current record.

REFERENCES

For more information on how to write custom DDX and DDV functions, see technical note 26 in the Visual C++ documentation.

For more information on using the CDaoRecordset and CRecordset classes, see the CDaoRecordset and CRecordset entries in the Visual C++ Class Library Reference.

Additional query words: CComboBox ClistBox combobox listbox
Keywords : MfcDAO MfcDatabase MfcUI kbfile kbsample
Version : WINDOWS:5.0,5.0sp1,5.0sp2,5.0sp3; WINNT:5.0,5.0sp1,5.0sp2,5.0sp3
Platform : WINDOWS winnt
Issue type : kbhowto

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Last reviewed: March 5, 1998
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