INFO: Data Access Objects Have Properties Based on Database Type

ID: Q129732

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 6.0
Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0
Microsoft Visual Basic Professional and Enterprise Editions, 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

Additional application-defined properties are available for Microsoft Access databases. For a complete list of built-in and application-defined properties, please see the following topics in the Microsoft Access Help menu:

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

The application-defined properties will not be a part of the DAO's Properties collection until the values are changed from their default values. You can change an application-defined property default value by using Visual Basic code or by using the Microsoft Access design environment. In Visual Basic code, use the CreateProperty method just as you would to create user-defined properties.

Steps to Display the Properties Collection

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

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

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

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

Run the program.

Additional query words: kbVBp400 kbVBp500 kbVBp600 kbdse kbDSupport kbVBp

Keywords : kbGrpVBDB
Version :
Platform : WINDOWS
Issue type : kbinfo