Using ADO with Microsoft Visual Basic

Setting up an ADO project and writing ADO code is similar whether you use Visual Basic or Visual Basic for Applications. This topic addresses using ADO with both Visual Basic and Visual Basic for Applications and notes any differences.

Referencing the ADO Library

The ADO library must be referenced by your project.

To reference ADO from Microsoft Visual Basic

1. In Visual Basic, from the Project menu, select References....
2. Select Microsoft ActiveX Data Objects x.x Library from the list. Verify that at least the following libraries are also selected:
   • Visual Basic for Applications
   • Visual Basic runtime objects and procedures
   • Visual Basic objects and procedures
   • OLE Automation
3. Click OK.

You can use ADO just as easily with Visual Basic for Applications, using Microsoft Access, for example.

To reference ADO from Microsoft Access

1. In Microsoft Access, select or create a module from the Modules tab in the Database window.
2. From the Tools menu, select References....
3. Select Microsoft ActiveX Data Objects x.x Library from the list. Verify that at least the following libraries are also selected:
   • Visual Basic for Applications
   • Microsoft Access 8.0 Object Library (or later)
   • Microsoft DAO 3.5 Object Library (or later)
4. Click OK.

Creating ADO Objects in Visual Basic

To create an automation variable and an instance of an object for that variable, you can use two methods: Dim or CreateObject.

Dim

You can use the New keyword with Dim to declare and instantiate ADO objects in one step:

Dim conn As New ADODB.Connection

Alternately, the Dim statement declaration and object instantiation can also be two steps:

Dim conn As ADODB.Connection
Set conn = New ADODB.Connection

Note It is not required to explicitly use the ADODB progid with the Dim statement, assuming you have properly referenced the ADO library in your project. However, using it ensures that you won't have naming conflicts with other libraries.

For example, if you include references to both ADO and DAO in the same project, you should include a qualifier to specify which object model to use when instantiating Recordset objects, as in the following code:

Dim adoRS As ADODB.Recordset
Dim daoRS As DAO.Recordset

CreateObject

With the CreateObject method, the declaration and object instantiation must be two discrete steps:

Dim conn1
Set conn1 = CreateObject("ADODB.Connection") As Object

Objects instantiated with CreateObject are late-bound, which means that they are not strongly typed and command-line completion is disabled. However, it does allow you to skip referencing the ADO library from your project, and enables you to instantiate specific versions of objects. For example:

Set conn1 = CreateObject("ADODB.Connection.2.0") As Object

You could also accomplish this by specifically creating a reference to the ADO version 2.0 type library and creating the object.

Instantiating objects with the CreateObject method is typically slower than using the Dim statement.

Handling Events

In order to handle ADO events in Microsoft® Visual Basic®, you must declare a module-level variable using the WithEvents keyword. The variable can be declared only as part of a class module and must be declared at the module level. For a more complete discussion of handling ADO events, see Chapter 7: Handling ADO Events.

Visual Basic Examples

Many Visual Basic examples are included with the ADO documentation. For more information, see ADO Code Examples in Microsoft Visual Basic.

See Also

ActiveX Data Objects Start Page | Using ADO with Microsoft Visual C++ | Using ADO with Microsoft Visual J++ | Using ADO with Scripting Languages