C#

You can force a full cache flush by manually changing the the icon size yourself to something
one pixel smaller, broadcasting WM_SETTINGCHANGE and then setting the icon size back to normal again 
(obviously followed by another WM_SETTINGCHANGE). The message broadcast is typically done something 
like this:

   SendMessageTimeout(
     HWND_BROADCAST,
     WM_SETTINGCHANGE,
     SPI_SETNONCLIENTMETRICS,
     (LPARAM)"WindowMetrics",
     SMTO_NORMAL|SMTO_ABORTIFHUNG, 
     10000, NULL);

You alter the icon size by manually changing its value in the registry. The key to look at is:
   HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics 

The values for the icon size are Shell Icon Size and Shell Small Icon Size (both are stored as 
strings - not DWORDs). You only need to change one of them to cause the refresh to happen (typically 
the large icon size). If those values don't exist, the shell uses the SM_CXICON metric 
(GetSystemMetrics) as the default size for large icons, and half of that for the small icon size. If 
you're trying to cause a refresh and the registry entry doesn't exist, you can just assume that the 
size is set to SM_CXICON.

static void RefreshIconCache()
        {

         // get the the original Shell Icon Size registry string value
            RegistryKey k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);
            Object OriginalIconSize = k.GetValue("Shell Icon Size");

         // set the Shell Icon Size registry string value
            k.SetValue("Shell Icon Size", (Convert.ToInt32(OriginalIconSize) + 1).ToString());
            k.Flush(); k.Close();
            
         // broadcast WM_SETTINGCHANGE to all window handles
            int res = 0;
            SendMessageTimeout(0xffff, 0x001A, 0, "", 0x0002, 5000, out res);
            //SendMessageTimeout(HWD_BROADCAST,WM_SETTINGCHANGE,0,"",SMTO_ABORTIFHUNG,5 seconds, return result to res)

         // set the Shell Icon Size registry string value to original value
            k = Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop").OpenSubKey("WindowMetrics", true);
            k.SetValue("Shell Icon Size", OriginalIconSize);
            k.Flush(); k.Close();

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

        }

mirko86 wrote:

but honestly i dont know what they were talking about with this