ACC: How to Create a Custom Database Version Using DAO

• Microsoft Access versions 2.0, 7.0

SUMMARY

Advanced: Requires expert coding, interoperability, and multiuser skills.

This article demonstrates four user-defined functions that you can use to control a custom database's version number, and then shows you how to use the functions to manage your databases' version numbers. These functions are useful when you need to know the specific version of your database application before you perform a task.

This article assumes that you are familiar with Visual Basic for Applications and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information about Visual Basic for Applications, please refer to the "Building Applications with Microsoft Access for Windows 95" manual.

NOTE: Visual Basic for Applications (used in Microsoft Access for Windows 95 version 7.0) is called Access Basic in version 2.0. For more information about Access Basic, please refer to the "Building Applications" manual.

MORE INFORMATION

The Properties collection in a Microsoft Access database applies to all objects in that database, such as forms, reports, tables, and so on. They are assigned by Microsoft Access and the developer through the user interface and when objects are created, modified, and saved. At the top level of the DAO (data access objects) model, the database contains properties that identify specific information concerning the version of the Microsoft Access database file format, the current Microsoft Access version, the database collating order, and so on.

The Properties collection supports the use of user-defined properties that can be appended to the Properties collection and used in functions.

To create the four functions that give you control over a custom database's version number, follow these steps:

1. Create a new module and type the following four functions.
   
   NOTE: In the following sample code, an underscore (_) at the end of a line is used as a line-continuation character. Remove the underscore from the end of the line when re-creating this code in Access Basic.

   
         ' **********************************************************
         ' Function: AddDBVersion()
         '  Purpose: Used to add a new Version property to the
         '           current database.
         '   Return: True(-1) for success, False(0) for failure.
         ' **********************************************************
   
   
         Function AddDBVersion (MyVersionNum As String) As Integer
   
            On Local Error GoTo AddDBVersion_Err
   
            Dim MyWS As WorkSpace
            Dim MyDB As Database
            Dim MyVersion As Property
   
            ' Set all DAO objects.
            Set MyWS = DBEngine.Workspaces(0)
            Set MyDB = MyWS.Databases(0)
   
            ' Assign and append the Version number.
            Set MyVersion = MyDB.CreateProperty("MyVersion", DB_TEXT, _
                            MyVersionNum)
            MyDB.Properties.Append MyVersion
   
            ' Pass back success.
            AddDBVersion = True
   
         AddDBVersion_End:
            Exit Function
   
         AddDBVersion_Err:
            MsgBox Error$
            Resume AddDBVersion_End
   
         End Function
   
         ' **********************************************************
         ' Function: UpdateDBVersion()
         '  Purpose: Used to edit the Version property in the
         '           current database.
         '   Return: True(-1) for success, False(0) for failure.
         ' **********************************************************
   
         Function UpdateDBVersion (MyVersionNum As String) As Integer
   
            On Local Error GoTo UpdateDBVersion_Err
   
            Dim MyWS As WorkSpace
            Dim MyDB As Database
   
            ' Set all DAO objects.
            Set MyWS = DBEngine.Workspaces(0)
            Set MyDB = MyWS.Databases(0)
   
            ' Edit the Version property.
            MyDB.Properties("MyVersion") = MyVersionNum
   
            ' Pass back success.
            UpdateDBVersion = True
   
         UpdateDBVersion_End:
            Exit Function
   
         UpdateDBVersion_Err:
            MsgBox Error$
            Resume UpdateDBVersion_End
   
         End Function
   
         ' ***********************************************************
         ' Function: GetDBVersion()
         '  Purpose: Used to return the Version property to the
         '           calling routine or expression.
         '   Return: Version for success, an empty string for failure.
         ' ***********************************************************
   
         Function GetDBVersion () As String
   
            On Local Error GoTo GetDBVersion_Err
   
            Dim MyWS As WorkSpace
            Dim MyDB As Database
   
            ' Set all DAO objects.
            Set MyWS = DBEngine.Workspaces(0)
            Set MyDB = MyWS.Databases(0)
   
            ' Return the version number.
            GetDBVersion = MyDB.Properties("MyVersion")
   
         GetDBVersion_End:
            Exit Function
   
         GetDBVersion_Err:
            MsgBox Error$
            Resume GetDBVersion_End
   
         End Function
   
         ' **********************************************************
         ' Function: DeleteDBVersion()
         '  Purpose: Used to remove the Version property from the
         '           current database.
         '   Return: True(-1) for success, False(0) for failure.
         ' **********************************************************
   
         Function DeleteDBVersion () As Integer
   
            On Local Error GoTo DeleteDBVersion_Err
   
            Dim MyWS As WorkSpace
            Dim MyDB As Database
            Dim MyVersion As Property
   
            ' Set all DAO objects.
            Set MyWS = DBEngine.Workspaces(0)
            Set MyDB = MyWS.Databases(0)
   
            ' Delete the Version property.
            MyDB.Properties.Delete "MyVersion"
   
            ' Pass back success.
            DeleteDBVersion = True
   
         DeleteDBVersion_End:
            Exit Function
   
         DeleteDBVersion_Err:
            MsgBox Error$
            Resume DeleteDBVersion_End
   
         End Function 




2. To use the functions, use the following code in an event procedure or your specific code.
   
   
   • To create a version number:

     
              If AddDBVersion("1.00") Then
                 MsgBox "Version Number Created"
              Else
                 MsgBox "Unable to Change Version Number "
              End If 

   
   
   
   • To edit a version number:

     
              If UpdateDBVersion("2.00") Then
                 MsgBox "Version Number Updated"
              Else
                 MsgBox "Unable to Change Version Number "
              End If 

   
   
   
   • To return a version number:
     
     MsgBox "Version Number is " & GetDBVersion()
   
   
   
   • To return a version number on a form or report:
     
     Create a Text Control and set the control's ControlSource property to =GetDBVersion()
   
   
   
   • To delete a version number:

     
              If DeleteDBVersion() Then
                 MsgBox "Version Number Deleted"
              Else
                 MsgBox "Unable to Delete Version Number"
              End If 

   
   
   

REFERENCES

Microsoft Access "Building Applications," version 2.0, Chapter 5, "Access Basic Fundamentals," pages 113-132

Microsoft Access "Building Applications," version 2.0, Chapter 7, "Objects and Collections," pages 174-181

For more information about the CreateProperty, search for "CreateProperty," and then "CreateProperty Method (Data Access)" using the Microsoft Access Help menu.

Additional query words:

Keywords : kbprg MdlDao
Version : WINDOWS:2.0,7.0
Platform : WINDOWS
Issue type : kbhowto