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Editorial Team
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Asked: 2026-05-13T21:23:20+00:00

I have both InDesign CS2 and CS3 installed. Both use files with .indd extension.

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I have both InDesign CS2 and CS3 installed. Both use files with .indd extension. How does Windows know which icon to use? It uses correct icons i.e. CS2 files have cs2 icon and CS3 files have CS3 icon.

How does Windows know how to do this?

And how can I extract or use this version-detection system in my programs?

Edit:

Thank you for your shell-extension-icon-handler answers. Something new to me. But is there any way I could connect to IconHandler that InDesign provides and use it to detect version of the InDesign file?

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1 Answer

  1. Editorial Team

    You need to write an Icon Handler shell extension. See the MSDN documentation for IExtractIcon. The basic mechanism is that you create a shell extension and register the icon handler for the file type you want (look in HKEY_CLASSES_ROOT/.indd) and then the shell loads your handler, passes the file information and requests an icon in return. There’s also the IExtractImage method if you want to provide a thumbnail bitmap rather than just an icon.

    Note that you need to be especially careful writing shell extension handlers as any memory leaks or crashes can nuke the explorer and any other applications that display a file open/save dialog.

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