Programming Forums - Changing icons problem

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Changing icons problem

Hi there.
I have a problem. When I change the default icon for some file extension, I need it to happen instantly. For example, I want to change icon for .cdc files. I know how to do it, and that is not a problem, but the problem is that it doesn't happen instantly, but when some kind of system refresh happens. I think it has something to do with shelliconcache.dll or iconcache.db, witch i can't find on my system. I have WXP Professional.
For example, when you start BS Player and assign it to be the default player for some file types, it happens, and all icons change right away.
I need to know what I can do to make this change happening when I want it. What is the thing that BS player and Windows Media Player do when they make a registry change, to make it happen at that exact moment?
The thing is that i am creating an application that should be able to do this, and i have no idea what should be done, and how BS Player does it.
Maybe I need to send some kind of system message to tell the OS to reload icon cache.
Any help would be most appreciated.
Thanks.

@The Dark: I'd have to say, that link is far from useful.

I haven't been able to find a good answer. Odd.

I know that the tweakUI powertool rebuilds your icons just for that purpose.
I think you need to do the same.

@Dameon: Really? The first link off google (the codeproject one) shows a similar problem with changing the icons and shows the exact call needed to get the icon cache to be refreshed.

 ::SendMessage(HWND_BROADCAST ,

        WM_SETTINGCHANGE,SPI_SETNONCLIENTMETRICS,NULL);

I suspect that there is a better SPI_ value for icon changing, but this one (suposedly) does the trick.

Guys, thank you all for helping, especially The Dark (again).
You got it right, but i still have a problem.
ShellIconChanger really works, and it does what my app needs to do, but i have problems implementing the same in C#.

Here is what happens:

[DllImport("user32.dll")]

        public static extern uint SendMessage(IntPtr hWnd, uint Msg, uint wParam, IntPtr lParam);

RegistryKey k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);

k.SetValue("Shell Icon Size", "33");  //this value in my reg is 32

k.Flush(); k.Close();



SendMessage((IntPtr)0xffff, 0x001A, 0x002A, IntPtr.Zero);



k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);

k.SetValue("Shell Icon Size", "32");  //back to what it was

k.Flush(); k.Close();



SendMessage((IntPtr)0xffff, 0x001A, 0x002A, IntPtr.Zero);

App always blocks on second call to SendMessage function.
Icons sometimes change immediately, and sometimes don't.
From my app, icons change immediately only when I start it after doing the same thing in ShellIconChanger. Every other time app fails to do this.
What am I missing?

It may be the fault of another program you are running. If an app doesn't respond to the global SendMessage, it sits there waiting for it for a period of time. I am not sure what you can do about it though.

Use PostMessage instead?

Sorry about the criticism of the link. I seem to have missed the first result...somehow.

It works! The SendMessageTimeout function does the trick.

private static extern long SendMessageTimeout(

        int hWnd,

        int Msg,

        int wParam,

        string lParam,

        int fuFlags,

        int uTimeout,

        out int lpdwResult

);

RegistryKey k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);

k.SetValue("Shell Icon Size", "33");

k.Flush(); k.Close();



int res = 0;

SendMessageTimeout(0xffff, 0x001A, 0, "", 0x0002, 5000, out res);



k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);

k.SetValue("Shell Icon Size", "32");

k.Flush(); k.Close();



SendMessageTimeout(0xffff, 0x001A, 0, "", 0x0002, 5000, out res);

This function specifies the timeout period. After 5 seconds (in this case) program returns from the function, and icons are reloaded.
I still don't understand why the program never returned from SendMessage function, but it's not so important.
Thanks a lot.