Microsoft KB Archive/129929

= How to Respond to Auto-commit Feature of VB Data Control =

Article ID: 129929

Article Last Modified on 1/8/2003

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APPLIES TO


 * Microsoft Visual Basic 4.0 Standard Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 16-bit Enterprise Edition
 * Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
 * Microsoft Visual Basic 3.0 Professional Edition
 * Microsoft Visual Basic 3.0 Professional Edition

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This article was previously published under Q129929



SUMMARY
When you perform any of the following actions on a Visual Basic Data Control, any changes to controls bound to the Data Control are automatically committed to the Database:


 * Move off of the current record with any of the Move methods (MoveFirst, MovePrevious, MoveNext, MoveLast, or Move).
 * Move off of the current record using the VCR-like buttons of the Data Control.
 * Add a new record with the AddNew method.
 * Update a record that is being edited or added with the Update method. Note that this is not the UpdateRecord method.
 * Delete the current record with the Delete method.
 * Move off the current record with any of the Find methods (FindFirst, FindNext, FindPrevious, FindLast, or Seek). This only applies to the Table-type RecordSet object.
 * Move off the current record by setting the Bookmark property.
 * Close the RecordSet with the Close method.
 * Unload the form that the data control is on.

This article shows how to use the Action parameter of the Data Control's Validate event to respond to this automatic commit.



MORE INFORMATION
The Action argument passes to the Sub procedure the action taking place on the Data Control. If you use a Select Case statement on the Action parameter, you can choose the events to which you want to respond.

The Validate event occurs before the next record becomes active. The action that causes the Validate to be fired can be cancelled by setting the Action parameter to vbDataActionCancel. The saving of the data can be cancelled by setting the Save parameter in the Validate event to False. And you can choose not to save bound control values individually by changing the DataChanged property (which all bindable controls have) to False for the individual controls.

If you want to roll back all the changes of an editing session, you can place BeginTrans and Commitrans (or Rollback) statements around your Data Control code. However, the following example code gives you better control.

Step-by-Step Example
 Start a new project in Visual Basic. Form1 is created by default. Add a Data Control (Data1) and two Text Boxes (Text1 and Text2) to Form1.  Set the following properties of the controls:   Control     Property          Value --  Data1       DatabaseName      Biblio.mdb Data1      RecordSource      PUBLISHERS Text1      DataSource        Data1 Text1      DataField         Name Text2      DataSource        Data1 Text2      DataField         City   Add the following code to the Data1_Validate event: Sub Data1_Validate (Action As Integer, Save As Integer) Dim RC As Integer Debug.Print "Action "; Action; " generated the Validate event." If Save Then Select Case Action Case vbDataActionFind, _ vbDataActionDelete, _ vbDataActionAddNew, _ vbDataActionCancel, _ vbDataActionClose 'No action Case vbDataActionMoveNext, _ vbDataActionMovePrevious, _ vbDataActionMoveFirst, _ vbDataActionMoveLast, _ vbDataActionUnload RC = MsgBox("Save changes to current record?", vbYesNo + _                 vbQuestion) If RC = vbNo Then Save = False Debug.Print "The data will NOT be saved." Else If Not IsValid Then ' Write your own IsValid Function to return T/F value ' and do any additional validation that you want. Action = vbDataActionCancel End If              End If            Case Else ' This case should never be executed unless a new ' (unhandled) value is added to the Action parameter. End Select End If  End Sub

Function IsValid As Boolean IsValid = True ' Write your own validation routine here. End Function  Start the program by choosing Start from the Run menu or by pressing the F5 key. Make changes to the Text boxes.</li> Move off the current record by using the Data control buttons.</li></ol>

The current behavior is that you are prompted to save or not save the data. You can easily modify this to do any internal validation checking that you need as long as within the Validation event you do not use any of the methods described at the beginning of this article to generate another change in the current record.

Additional query words: 4.00 vb4win vb4all

Keywords: KB129929

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