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Q120682: How to Exclude CLSIDs from OLE’s Insert Object Dialog

Article: Q120682
Product(s): Microsoft C Compiler
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 29-JUL-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - Microsoft Visual C++ for Windows, 16-bit edition, version 1.5 
   - Microsoft Visual C++, 32-bit Editions, version 2.0 
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SUMMARY
=======

When building a container/server application with the Microsoft Foundation OLE
Classes, you should prohibit the application user from inserting an object of
the type serviced by the application itself. In fact, with an MDI application,
if you try to embed your server's object in your server's document, you'll get
the following message and trace messages indicating that a QueryInterface call
failed:

Message box statement:

  

  Failed to create object. Make sure that the object is entered
  in the system registry.

Trace messages:

  

  Warning: constructing COleException, scode = E_NOINTERFACE ($80000004)
  Warning: Throwing an Exception of type COleException"

This article gives an example showing how to customize the OLE Insert Object
dialog wrapped by the COleInsertDialog class. This customization omits your
server object's class id from the selection list so the user won't be able to
embed it.

MORE INFORMATION
================

The COleInsertDialog class contains a member m_io -- as described in online help
for the OLE Classes:

  COleInsertDialog::m_io

  Structure of type OLEUIINSERTOBJECT used to control the
  behavior of the Insert Object dialog box. Members of
  this structure can be modified either directly or
  through member functions.

The OLEUIINSERTOBJECT dialog contains two members which allow the user to exclude
specific object types from the dialog's selection list by CLSID. The member
lpClsidExclude is a pointer of type LPCLSID and therefore must point directly to
a variable of type CLSID. The member cClsidExclude is a UINT and contains the
number of CLSID types that are pointed to by lpClsidExclude. If you want to
exclude more than one CLSID, use an array.

The sample code below demonstrates how to exclude the AppWizard generated CLSID
for the application's own object. This CLSID can be found in the CWinApp-derived
class implementation file as the static global variable "clsid" and will look
something like this:

  // This identifier was generated to be statistically unique for your app.
  // You may change it if you prefer to choose a specific identifier.
  static const CLSID BASED_CODE clsid = {   0x565295c6, 0xc992, 0x11cd,
                          { 0x96, 0xf2, 0x0, 0xaa, 0x0, 0x3b, 0x80,0x67 } };

For the purpose of accessing clsid from a view class member function, take the
"static" storage class off the above declaration.

You can then assign the lpClsidExclude pointer to &clsid from any module in
the program. For the purpose of this sample, cClsidExclude is a count of one, so
no array will be used.

The code to assign these members must be run before displaying the dialog.
Therefore it's best to assign these members in the container view class'
OnInsertObject() member. The OnInsertObject() shown in the sample code below is
based on the one that AppWizard provides.

Sample Code
-----------

  /* AppWizard generated OnInsertObject() function modified to
   * exclude our own object type from the OLE Insert Object Dialog.
   */ 
  void CSvrcntrView::OnInsertObject()
  {
      // Invoke the standard Insert Object dialog box to obtain information
      //  for new CSvrcntrCntrItem object.
      COleInsertDialog dlg;
      // Our own object's clsid - don't insert it!
      dlg.m_io.lpClsidExclude = (LPCLSID) &clsid;
      dlg.m_io.cClsidExclude = 1;    // Number of clsid's in the array.

      if (dlg.DoModal() != IDOK)
          return;

      BeginWaitCursor();

      CSvrcntrCntrItem* pItem = NULL;
      TRY
      {
          // Create new item connected to this document.
          CSvrcntrDoc* pDoc = GetDocument();
          ASSERT_VALID(pDoc);
          pItem = new CSvrcntrCntrItem(pDoc);
          ASSERT_VALID(pItem);

          // Initialize the item from the dialog data.
          if (!dlg.CreateItem(pItem))
              AfxThrowMemoryException();  // any exception will do
          ASSERT_VALID(pItem);

          // If item created from class list (not from file) then launch
          //  the server to edit the item.
          if (dlg.GetSelectionType() == COleInsertDialog::createNewItem)
              pItem->DoVerb(OLEIVERB_SHOW, this);

         ASSERT_VALID(pItem);

          // As an arbitrary user interface design, this sets the selection
          //  to the last item inserted.

          // TODO: reimplement selection as appropriate for your application

          m_pSelection = pItem;   // set selection to last inserted item
          pDoc->UpdateAllViews(NULL);
      }
      CATCH(CException, e)
      {
          if (pItem != NULL)
          {
              ASSERT_VALID(pItem);
              pItem->Delete();
          }
          AfxMessageBox(IDP_FAILED_TO_CREATE);
      }
      END_CATCH

      EndWaitCursor();
  }

Additional query words: kbinf 1.50 2.00 2.50 3.00

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbMFC

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