PRB: GetObject or GetActiveObject Cannot Find a Running Office Application (238610)

MORE INFORMATION

In most situations, developers who want to automate an Office application need to use CreateObject (Visual Basic) or CoCreateInstance (Visual C++) to launch a new instance of the Office application.

However, there are cases where you might prefer to automate an Office application that is already running: for example, if the user previously started the Office application. Or, if you launched the Office application's executable using code so that you could specify command-line switches for the application. In order to automate the running Office application, you must use GetObject or GetActiveObject.

Steps to Reproduce Behavior

1. Start Microsoft Visual Basic and create a new Standard EXE project. Form1 is created by default.
2. Add a CommandButton control to Form1.
3. Add the following code to the form's code module:

   Private Sub Command1_Click()
       Dim oExcel As Object
       ' Launch a new instance of Microsoft Excel:
       Shell "C:\Program Files\Microsoft Office\Office\Excel.EXE", _
          vbMinimizedNoFocus
       ' An error 429 occurs on the following line:
       Set oExcel = GetObject(, "Excel.Application")
       MsgBox oExcel.Name
       Set oExcel = Nothing
   End Sub
   					

4. Make sure the location of the Excel.exe is correct in the code sample.
5. Quit Microsoft Excel if it is already running.
6. Press F5 to run the project, and click Command1.

Workaround

To work around the problem, you can:

• Give focus to the Office application by changing the second argument of the Shell function to either vbMinimizedFocus, vbMaximizedFocus, or vbNormalFocus.
  
  
• Give your Visual Basic form the focus.
  
  
• And finally, attempt GetObject while accounting for the Office application's load time.

The following revised code illustrates this workaround:

Private Declare Sub Sleep Lib "kernel32" _
    (ByVal dwMilliseconds As Long)

Private Sub Command1_Click()
    Dim intSection As Integer
    Dim intTries As Integer
    Dim oExcel As Object
    
    ' Enable error handler for this procedure:
    On Error GoTo ErrorHandler
    
    ' Launch Microsoft Excel, giving it focus:
    Shell "C:\Program Files\Microsoft Office\Office\Excel.EXE", _
        vbMinimizedFocus 'other options for starting with
        'focus: vbMaximizedFocus and vbNormalFocus
    
    ' Move focus back to this form. (This ensures the Office
    '  application registers itself in the ROT, allowing
    '  GetObject to find it.)
    Me.SetFocus
    
    ' Attempt to use GetObject to reference the running
    '  Office application:
    intSection = 1 'attempting GetObject...
    Set oExcel = GetObject(, "Excel.Application")
    intSection = 0 'resume normal error handling
    
    ' Now you can automate Microsoft Excel:
    MsgBox oExcel.Name & ": able to GetObject after " & _
        intTries + 1 & " tries.", vbMsgBoxSetForeground
    
    ' Finished with automation so release your reference:
    Set oExcel = Nothing
    
    ' Exit procedure:
    Exit Sub
    
ErrorHandler:
    If intSection = 1 Then 'GetObject may have failed because the
    'Shell function is asynchronous; enough time has not elapsed
    'for GetObject to find the running Office application. Wait
    'wait 1/2 seconds and retry the GetObject. If you try 20 times
    'and GetObject still fails, assume some other reason
    'for GetObject failing and exit the procedure.
        intTries = intTries + 1
        If intTries < 20 Then
            Sleep 500 ' wait 1/2 seconds
            Resume 'resume code at the GetObject line
        Else
            MsgBox "GetObject still failing. Process ended.", _
                vbMsgBoxSetForeground
        End If
    Else 'intSection = 0 so use normal error handling:
        MsgBox Error$
    End If
End Sub
				

Workaround for C++

If you are programming in C++, the following code sample demonstrates a similar workaround as shown in the above Visual Basic sample. Notice that SetForegroundWindow() is used to move focus away from Excel, allowing it to register its running objects:

//Store the handle of the currently active window...
HWND hwndCurrent = ::GetForegroundWindow();

//Launch Excel and wait until it is waiting for
//user input...
STARTUPINFO Start;
PROCESS_INFORMATION ProcInfo;
ZeroMemory(&Start,sizeof(STARTUPINFO));
Start.cb=sizeof(Start);
Start.dwFlags = STARTF_USESHOWWINDOW;
Start.wShowWindow = SW_SHOWMINIMIZED;

//Change the path to Excel as needed...
LPSTR pszExcelPath = 
      "c:\\program files\\microsoft office\\office\\excel.exe";

::CreateProcess(NULL, pszExcelPath, 0, 0, 1,
       NORMAL_PRIORITY_CLASS, 0, NULL, &Start, &ProcInfo);


if((::WaitForInputIdle(ProcInfo.hProcess, 10000))==WAIT_TIMEOUT)
{
    ::MessageBox(NULL, "Timed out waiting for Excel.", NULL,  
                 MB_OK);
}

//Restore the active window to the foreground...
//  NOTE: If you comment out this line, the code will fail!
::SetForegroundWindow(hwndCurrent);

//Initialize COM library...
::CoInitialize(NULL);

//Attach to the running instance...
CLSID clsid;
CLSIDFromProgID(L"Excel.Application", &clsid);  
IUnknown *pUnk = NULL;
IDispatch *pDisp = NULL;

for(int i=1;i<=5;i++) //try attaching for up to 5 attempts
{
   HRESULT hr = GetActiveObject(clsid, NULL, (IUnknown**)&pUnk);
   if(SUCCEEDED(hr)) 
   {
       hr = pUnk->QueryInterface(IID_IDispatch, (void **)&pDisp);
       break;
   }
   ::Sleep(1000);
}
        
if (!pDisp) {
    ::MessageBox(NULL, "Failed to find instance!!", "Error", 
                 MB_ICONHAND);
}
else {
    ::MessageBox(NULL, "Got instance of Excel!", "Success", MB_OK);
}

//Release the no-longer-needed IUnknown...
if (pUnk) 
    pUnk->Release();

//... Add your automation code for Excel here ...

//Release pDisp when no longer needed...
if (pDisp)
    pDisp->Release();

//Cleanup COM...
CoUninitialize();