• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SYMPTOMS

When you use the Shell_NotifyIcon function or the SysTray control sample from the Visual Basic CD-ROM, you may receive the following error message:

Run-time error: -2147417843 (8001010d)
Automation Error

CAUSE

The run-time error occurs because you are trying to make an Automation call to an out-of-process (ActiveX) EXE from within the event notification of the Taskbar Notification Area callback. The value -2147417843 translates to the following error message:

An outgoing call cannot be made since the application is dispatching an input-synchronous call.

RESOLUTION

Avoid making outgoing Automation calls during the Taskbar Notification Area callback. If an Automation method needs to be called in response to a user event involving the Taskbar Notification Area, use a simple Timer to post yourself a message, and then let the callback function complete. When the Timer event fires, you can safely call your Automation method.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

1. Copy the SysTray control sample from the Tools\Unsupprt folder of the Visual Basic 5.0 CD-ROM, or the Common\Tools\VB\Unsupprt folder of the Visual Basic 6.0 CD-ROM, to your hard drive.
   
   
2. Open the project and compile the control. When complete, close the project.
   
   
3. Create a new Standard EXE project. Form1 is created by default.
   
   
4. From the Project menu, click Components, and check System Tray Icon Control. Click OK.
   
   
5. Select the SysTray control in the toolbox and add an instance to Form1.
   
   
6. Add the following code into Form1's code window:
   
   

   Option Explicit
   Private oWord As Object
   
   Private Sub Form_Load()
      Set oWord = CreateObject("Word.Application")
      Set cSysTray1.TrayIcon = Me.Icon
      cSysTray1.InTray = True
   End Sub
   
   Private Sub Form_Unload(Cancel As Integer)
      cSysTray1.InTray = False
      Set oWord = Nothing
   End Sub
   
   Private Sub cSysTray1_MouseDblClick(Button As Integer, Id As Long)
      oWord.Visible = True
   End Sub 

7. Run the application by pressing the F5 key. The error occurs when you double-click the application's icon in the System Tray. Press the END key to stop the debugger.
   
   
8. To avoid the error, add a Timer to Form1.
   
   
9. Replace the code in Form1 with the following:
   
   

   Option Explicit
   Private oWord As Object
   
   Private Sub Form_Load()
      Set oWord = CreateObject("Word.Application")
      Set cSysTray1.TrayIcon = Me.Icon
      cSysTray1.InTray = True
      Timer1.Enabled = False
      Timer1.Interval = 10
   End Sub
   
   Private Sub Form_Unload(Cancel As Integer)
      cSysTray1.InTray = False
      Set oWord = Nothing
   End Sub
   
   Private Sub cSysTray1_MouseDblClick(Button As Integer, Id As Long)
      Timer1.Enabled = True
   End Sub
   
   Private Sub Timer1_Timer()
      Timer1.Enabled = False
      oWord.Visible = True
   End Sub 

10. Re-run the application by pressing the F5 key. This time no error should occur.
    
    

REFERENCES

For additional information about input-synchronous calls in COM and this Automation error, click the article number below to view the article in the Microsoft Knowledge Base:

Q131056 PRB: Synch OLE Call Fails in Inter-Process/Thread SendMessage

Q176085 HOWTO: Use the Taskbar Notification Area Directly from Visual Basic 5.0

Additional query words:

Keywords : kbAutomation kbVBp kbVBp500 kbVBp600 kbGrpVB kbDSupport kbofficeprog
Issue type : kbprb
Technology :

Article ID: Q190523

Last Reviewed:
October 25, 2000

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