PRB: Automation Error (-2147417843) Using the System Tray

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

SYMPTOMS

When using the Shell_NotifyIcon API 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 system tray 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 System Tray callback. If an Automation method needs to be called in response to a user event involving the System Tray, 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 directory of the Visual Basic 5.0 CD-ROM, or the Common\Tools\VB\Unsupprt directory 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 will occur when you double-click the application's icon in the System Tray. Press END 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, please see the following article in the Microsoft Knowledge Base:

Q176085 : HOWTO: Use the System Tray Directly from Visual Basic 5.0

Additional query words: kbVBp kbdsd kbDSupport kbVBp500 kbVBp600 kbAutomation

Keywords          : 
Version           : 
Platform          : WINDOWS 
Issue type        : kbprb 

Last Reviewed: May 25, 1999