IconHandler Shell Extension is being overridden by default program

Question

I created an IconHandler shell extension for my program. It handles icons for .plan files.  

This works fine if .plan is not registered with a default program. But once it is, the icon is overridden with the icon for the executable.

I can delete the UserChoice key in  Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.plan

, but then my extension is no longer associated.

Basically I want to associate an extension with a program AND use my IconHandler for custom icons.

What can I do?

Answer 1

First, you should read and study https://www.codeproject.com/Articles/797/The-Complete-Idiots-Guide-to-Writing-Shell-Exten.

Then download the sample code and build the Icon Handler for the txtfile file type.  On my system where notepad.exe was registered as the default program for text files the demo Icon Handler still provided the icons displayed by explorer.  The sample code is quite old so you may need to tweak it a little bit to get it to build with modern versions of Visual Studio and ATL.

Answer 2

icon handler is part of the file association. DefaultIcon must be %1 for your handler to work, when it gets overwritten by another program to "exefilename, resourceid", your icon handler will stop working. 

UserChoice is created to prevent you from taking the file association back programmatically. The file association is the user's choice, not yours. Best you can do is to register your file association then hope the user would choose you over the other program. 

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Visual C++ MVP

Answer 3

icon handler is part of the file association. DefaultIcon must be %1 for your handler to work, when it gets overwritten by another program to "exefilename, resourceid", your icon handler will stop working. 

Sounds like the likely culprit.  In my quick and dirty test the default program was selected before the icon handler was registered.