Set Properties of Data Access Objects in Visual Basic

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Data Access Objects (DAO) enable you to manipulate the structure of your database and the data it contains from Visual Basic. Many DAO objects correspond to objects that you see in your database — for example, a TableDef object corresponds to a Microsoft Access table. A Field object corresponds to a field in a table.

Most of the properties you can set for DAO objects are DAO properties. These properties are defined by the Microsoft Jet database engine and are set the same way in any application that includes the Jet database engine. Some properties that you can set for DAO objects are defined by Microsoft Access, and aren't automatically recognized by the Jet database engine. How you set properties for DAO objects depends on whether a property is defined by the Jet database engine or by Microsoft Access.

Setting DAO Properties for DAO Objects

To set a property that's defined by the Jet database engine, refer to the object in the DAO hierarchy. The easiest and fastest way to do this is to create object variables that represent the different objects you need to work with, and refer to the object variables in subsequent steps in your code. For example, the following code creates a new TableDef object and sets its Name property:

  Dim dbs As DAO.Database
Dim tdf As DAO.TableDef
Set dbs = CurrentDb
Set tdf = dbs.CreateTableDef
tdf.Name = "Contacts"

Setting Microsoft Access Properties for DAO Objects

When you set a property that's defined by Microsoft Access, but applies to a DAO object, the Jet database engine doesn't automatically recognize the property as a valid property. The first time you set the property, you must create the property and append it to the Properties collection of the object to which it applies. Once the property is in the Properties collection, it can be set in the same manner as any DAO property.

If the property is set for the first time in the user interface, it's automatically added to the Properties collection, and you can set it normally.

When writing procedures to set properties defined by Microsoft Access, you should include error-handling code to verify that the property you are setting already exists in the Properties collection. See the Help topic about the CreateProperty method or the individual property topic for more information.

Keep in mind that when you create the property, you must correctly specify its Type property before you append it to the Properties collection. You can determine the Type property based on the information in the Settings section of the Help topic for the individual property. The following table provides some guidelines for determining the setting of the Type property.

The following table lists some Microsoft Access–defined properties that apply to DAO objects.