Snap-In Interface Technology + Embedded MFC GUI into ATL Server DLL

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This code in large borrowed from an article and code sample by
Steve Zimmerman "Create
Apps That Are Easily Extensible with Our Smart "Snap-Ins"
.   Its been updated to work with
ATL 3.0 and VC 6.0, plus a few extra modifications and
demonstartions of the coolest technologies :).

To see this sample code in action run the ComSnapin.exe. Your
screen will look like this:

It has only 4 menu items: File; Edit; View; and Help.

Now run register.bat located in SnapinOne\ReleaseMinSize
directory. This batch file will register SnapinOne.dll with the
system. Run ComSnapin.exe again. Your screen should look like

There ia a new menu item: Snapin Commands. If you click on the
menu item a Doc-View window will popup. This Doc/view framework
is entirely confined inside SnapinOne.dll which is a ATL dll

If you run unregister.bat which will unregister SnapinOne.dll
and excute program again you’ll see that the menu item gone.

SnapinOne.dll can communicate with parent application via
callback interfaces and obtain from it whatever information it
tries to digest.

This gives your "Snapin" enabled parent program
virtualy unlimited scalability.


  1. Create a regular MFC exe application framework with App
  2. Include in your project files: ISnapin.h,
    ISnapinCallbacks.h, SnapFrm.cpp, SnapFrm.h,   SnapIn.cpp,
  3. Derive CMainFrame class from CSnapInFrame instead of
    CFrameWnd (or CMDIFrameWnd). Easiest way would to add
    thisl line right above CMainFrame delaration:  #define CFrameWnd CSnapInFrame
  4. Your application is now fully Snap-In ready!

Snap In:

  1. Create a ATL COM Project with ATL App Wizard.  Add
    it to a current workspace Select it to be a DLL with MFC
  2. Add ATL class to this project (for instance CSnapinOne).
  3. Replace base ISnapinOne to ISnapIn, so the class is
    derived from ISnapIn interface instead.


Download compiled demo – 11 Kb
Download source code for demo project – 63 Kb

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