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Microsoft KB Archive/172381

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Knowledge Base


Article ID: 172381

Article Last Modified on 7/15/2004



APPLIES TO

  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • 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



This article was previously published under Q172381

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 the current record with any of the Move methods (MoveFirst, MovePrevious, MoveNext, MoveLast, or Move).
  • Move off 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 the action that is taking place on the Data Control to the Sub procedure. 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. You can cancel the saving of the data by setting the Save parameter in the Validate event to False. Also, 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

  1. Start a new project in Visual Basic. Form1 is created by default.
  2. Add a Data Control (Data1) and two Text Boxes (Text1 and Text2) to Form1.
  3. 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
    
                            
  4. 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
    
                            
  5. Start the program by choosing Start from the Run menu or by pressing the F5 key.
  6. Make changes to the Text boxes.
  7. Move off the current record by using the Data control buttons.

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


Additional query words: kbVBp500 kbVBp600 kbdse kbDSupport kbVBp kbCtrl kbVBp400

Keywords: kbhowto KB172381