FIX: Cannot Dynamically Add a Non-Licensed MFC Control

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

SYMPTOMS

When attempting to dynamically add an MFC ActiveX control to a Visual Basic project, you may receive the following error message in the compiled project:

Run-time error '747':
No design-time license information is found for control 'XX.YY'. Contact the vendor for control 'XX.YY' to obtain a design-time license.

CAUSE

When adding a new control to a Form or UserControl dynamically at run-time, Visual Basic queries the control for the IClassFactory2 interface. This interface is generally used by controls that require licensing. If the control supports this interface, Visual Basic will then attempt to create an instance of the control using the IClassFactory2::CreateInstanceLic method, passing the developer-provided license string as a parameter. If no license is required, an empty string is passed.

By default, all MFC ActiveX controls support the IClassFactory2 interface, even if the control does not require a design-time license. When Visual Basic makes the call to CreateInstanceLic, passing an empty string for the license, MFC returns the error CLASS_E_NOTLICENSED, indicating that the string passed is not a valid license key for this control. Visual Basic reports the error as an invalid or missing design-time license.

RESOLUTION

There are currently two workarounds for this problem:

1. If you add the MFC control to the Visual Basic IDE toolbox at design-time, and then uncheck the "Remove information about unused ActiveX controls" option on the Make tab of the Project|Properties dialog, Visual Basic will compile the licensing information of the control into your project. At run-time, Visual Basic will know that the control does not require a license, and therefore will call CreateInstance rather than CreateInstanceLic. This will avoid the error.



2. You can site the MFC control on a Visual Basic ActiveX control, expose its properties and methods, and then dynamically add the Visual Basic control at run-time.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

MORE INFORMATION

Steps to Reproduce Behavior

1. Start Visual C++. Create a new project and select MFC ActiveX Control Wizard. Name the project MFCTest.



2. From the Wizard Dialog, make sure the option "No run-time license" is selected and then click Next. From the "Which window class should this control subclass" drop-down box, select BUTTON. Then click Finish.



3. Build the MFC control by pressing the F7 key. The control will be registered on the system for you.



4. Open Visual Basic 6.0 and start a Standard EXE project. Form1 is created by default.



5. In the code window for Form1, add the following:




      Private m_MFCCtrl As VBControlExtender

      Private Sub Form_Load()
         Set m_MFCCtrl = Controls.Add("MFCTest.MFCTestCtrl.1", "xx", Me)
         m_MFCCtrl.Visible = True
      End Sub

   NOTE: If you chose a different name than "MFCTest" for your MFC project,
   you may need to change the ProgID passed to the Controls.Add method. 

6. Run the project once to see that Visual Basic can dynamically add the MFC control while debugging in the IDE.



7. Compile the Visual Basic project and run the compiled executable. You should receive the run-time error '747' on Form load.



8. To avoid the error, add your MFC control to the IDE toolbox before you compile the project. Click Components on the Project menu and check "MFCTest ActiveX control module" from the Components list. Click OK.



9. To make sure Visual Basic doesn't remove unused references at compile- time, select Project1 Properties from the Project menu and click the Make tab. Uncheck the "Remove information about unused ActiveX controls" option and then click OK.



10. Re-compile the project and run the compiled executable. The error should no longer occur.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

Q190670 HOWTO: Dynamically Add Controls to a Form with Visual Basic 6.0

Q188577 HOWTO: What is the Licenses Collection Used For?

Additional query words:

Keywords : kbservicepack kbActiveX kbCtrlCreate kbVBp kbVBp600bug kbVC kbVS600sp2 kbVS600SP1 kbVS600sp3fix
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbbug