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.

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, by 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. On 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.

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

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

Dim conn As New ADODB.Connection

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

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

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

System_CAPS_noteNote

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

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 by using the CreateObject method is typically slower than using the Dim statement.

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 thorough discussion of handling ADO events, see Handling ADO Events.

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

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