PRB: Can't Use ActiveForm to Reference Data Control in VB 3.0

- Microsoft Visual Basic programming system for Windows, version 3.0

SYMPTOMS

Using the ActiveForm Property of the Screen control or an MDI Parent form to reference a Data control causes a "Type Mismatch" error in Visual Basic.

CAUSE

This behavior is by design. This is not a bug in Visual Basic. The Visual Basic environment does not know in advance that the Active form will actually contain a Data control, so it generates a "Type mismatch" error.

WORKAROUND

To avoid the error message, use global objects to reference the local controls. The "More Information" section below demonstrates one method for doing this.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Correct Problem

1. Add the following code to the Form_Activate Event:

      Sub Form_Activate ()
         Set CurrentDS = Data1.Recordset
      End Sub
   
   

2. Change two lines of code into comments by adding a single quotation mark to the beginning of the line. Change the Set CurrentDS statement in the Set_CurrentDS Sub in Module1 to a comment, and do the same to the Call Set_CurrentDS statement in the Form_Click event of Form1.

Steps to Reproduce Problem

1. Start Visual Basic or from the File menu, choose New Project (ALT, F, N) if Visual Basic is already running. Form1 is created by default.

2. Add a data control (Data1) to Form1.

3. Set the DatabaseName Property of Data1 to BIBLIO.MDB.

4. From the File menu, choose New Module (ALT, F, M). Module1 is created.

5. Add the following code to the General section of Module1:

   Global CurrentDS As DynaSet

6. Add the following code to Module1:

      Sub Set_CurrentDS ()
         Set CurrentDS = Screen.ActiveForm.Data1.Recordset
      End Sub
   
   

7. Add the following code to the Form_Click event procedure of Form1:

      Sub Form_Click ()
         Call Set_CurrentDS
      End Sub
   
   

8. From the Run menu, choose start (ALT, R, S) or press the F5 key.