INFO: Data Access Objects Have Properties Based on Database Type

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0
• Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

Certain Visual Basic Data Access Objects (DAO), such as the Field, Recordset, and TableDef objects, each have a Properties collection that uniquely characterizes an instance of the object. You can use the default (built-in) properties in the collection or you can create user-defined properties by using the CreateProperty method.

The default properties available in the collection vary depending on the database type. A set of extended properties, referred to as application- defined properties, are available with Microsoft Access databases.

MORE INFORMATION

The built-in properties are available in the Properties collection for all databases including Microsoft Access, Btrieve, dBASE, Microsoft FoxPro, Paradox, and ODBC client-server databases such as SQL Server. For example, the following built-in properties are available in the Properties collection of the TableDef object (using DAO version 3.0):

    Name            SourceTableName
    Updatable       RecordCount
    DateCreated     ValidationRule
    LastUpdated     ValidationText
    Connect         ConflictTable
    Attributes

    Field Object, Fields Collection - Summary
    RecordSet Object, Recordsets Collection - Summary
    TableDef Object, TableDefs Collection - Summary

Steps to Display the Properties Collection

1. Start a new project in Visual Basic. Form1 is created by default.

2. If using Visual Basic 5.0, establish a reference to DAO 3.5 by clicking References from the Project menu.

3. Add the following code to the Form1_Click procedure:

         Dim MyDB As Database
         Dim MySet As Recordset
         Dim MyProperty As Property
         Dim MyTableDef as TableDef
   

         ' Access database
         Set MyDB = DBEngine.Workspaces(0).OpenDatabase("biblio.mdb")
         Set MySet = MyDB.OpenRecordset("Authors", dbOpenTable)
         Set MyTableDef = MyDB("Authors")
   

         'display properties collection for Field
         For Each MyProperty In MySet(0).Properties
            List1.AddItem MyProperty.Name
         Next
   
         'display properties collection for Recordset
         For Each MyProperty In Myset.Properties
            List2.AddItem MyProperty.Name
         Next
   
         'display properties collection for Tabledef
         For Each MyProperty In MyTableDef.Properties
            List3.AddItem MyProperty.Name
         Next
   
         'Append an application-defined TableDef property by
         'changing its default value so it appears in the list
         On Error GoTo myerr:     'if RowHeight property exists trap error
         Set MyProperty = MyTableDef.CreateProperty("RowHeight")
         MyProperty.Type = dbinteger
         MyProperty.Value = 9
         MyTableDef.Properties.Append MyProperty
   
         myerr:
         MsgBox("RowHeight Property already exists, Please create another")
   
         'Print list again to see that RowHeight is displayed
         For Each MyProperty In MyTableDef.Properties
            List4.AddItem MyProperty.Name
         Next
         MySet.Close
         MyDb.Close
         On Error GoTo 0
   
   

4. Add four list boxes (List1, List2, List3, and List4) to Form1.

5. Run the program.

Keywords          : APrgDataAcc APrgDataIISAM APrgDataODBC VB4ALL VB4WIN vb5all
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbinfo