How to refresh/reload Desktop

Question

I have a WPF C# project in which I'm implementing settings for Windows folder options. One of them is "Single-click to open an item" (instead of double-click). When I change the registry keys for that matter, I need to refresh Windows Explorer which I found a solution for. But desktop doesn't refresh, and even refreshing it manually doesn't apply the changes. I've used IActiveDesktop::ApplyChanges method but didn't work (or maybe I made a mistake). I've also used this code snippet, but it still doesn't apply the changes I've made:

SHChangeNotify(0x8000000, 0x1000, IntPtr.Zero, IntPtr.Zero);

And here is the full code snippet that I used for refreshing Windows Explorer (which is from this site):

[System.Runtime.InteropServices.DllImport("Shell32.dll")]
    private static extern int SHChangeNotify(int eventId, int flags, IntPtr item1, IntPtr item2);

    public static void RefreshWindowsExplorer()
    {
        // Refresh the desktop
        SHChangeNotify(0x8000000, 0x1000, IntPtr.Zero, IntPtr.Zero);

        // Refresh any open explorer windows
        // based on http://stackoverflow.com/questions/2488727/refresh-windows-explorer-in-win7
        Guid CLSID_ShellApplication = new Guid("13709620-C279-11CE-A49E-444553540000");
        Type shellApplicationType = Type.GetTypeFromCLSID(CLSID_ShellApplication, true);

        object shellApplication = Activator.CreateInstance(shellApplicationType);
        object windows = shellApplicationType.InvokeMember("Windows", System.Reflection.BindingFlags.InvokeMethod, null, shellApplication, new object[] { });

        Type windowsType = windows.GetType();
        object count = windowsType.InvokeMember("Count", System.Reflection.BindingFlags.GetProperty, null, windows, null);
        for (int i = 0; i < (int)count; i++)
        {
            object item = windowsType.InvokeMember("Item", System.Reflection.BindingFlags.InvokeMethod, null, windows, new object[] { i });
            Type itemType = item.GetType();

            // Only refresh Windows Explorer, without checking for the name this could refresh open IE windows
            string itemName = (string)itemType.InvokeMember("Name", System.Reflection.BindingFlags.GetProperty, null, item, null);
            if (itemName == "Windows Explorer")
            {
                itemType.InvokeMember("Refresh", System.Reflection.BindingFlags.InvokeMethod, null, item, null);
            }
        }
    }

That works for Windows Explorer but not the desktop (which is odd since desktop depends on explorer too). So how should I reload the desktop so that my changes take effect?

Answer 1

Thanks for all your replies and comments. I finally figured out a workaround for this problem. We could just hide all desktop icons and then show them again. This will force the desktop to reload.

Update: In Window 8, SHELLDLL_DefView is the child of one of WorkerW windows. (instead of Progman) So here is the updated code which works on Windows 8 and 8.1 too:

    [DllImport("user32.dll", SetLastError = true)]
    static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

    [DllImport("user32.dll", SetLastError = true)]
    static extern IntPtr GetWindow(IntPtr hWnd, GetWindow_Cmd uCmd);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

    enum GetWindow_Cmd : uint
    {
        GW_HWNDFIRST = 0,
        GW_HWNDLAST = 1,
        GW_HWNDNEXT = 2,
        GW_HWNDPREV = 3,
        GW_OWNER = 4,
        GW_CHILD = 5,
        GW_ENABLEDPOPUP = 6
    }

    private const int WM_COMMAND = 0x111;

    [DllImport("user32.dll", SetLastError = true)]
    static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

    private delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern int GetWindowText(IntPtr hWnd, StringBuilder strText, int maxCount);

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern int GetWindowTextLength(IntPtr hWnd);

    [DllImport("user32.dll")]
    private static extern bool EnumWindows(EnumWindowsProc enumProc, IntPtr lParam);

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);


    public static string GetWindowText(IntPtr hWnd)
    {
        int size = GetWindowTextLength(hWnd);
        if (size++ > 0)
        {
            var builder = new StringBuilder(size);
            GetWindowText(hWnd, builder, builder.Capacity);
            return builder.ToString();
        }

        return String.Empty;
    }

    public static IEnumerable<IntPtr> FindWindowsWithClass(string className)
    {
        IntPtr found = IntPtr.Zero;
        List<IntPtr> windows = new List<IntPtr>();

        EnumWindows(delegate(IntPtr wnd, IntPtr param)
        {
            StringBuilder cl = new StringBuilder(256);
            GetClassName(wnd, cl, cl.Capacity);
            if (cl.ToString() == className && (GetWindowText(wnd) == "" || GetWindowText(wnd) == null))
            {
                windows.Add(wnd);
            }
            return true;
        },
                    IntPtr.Zero);

        return windows;
    }

    static void ToggleDesktopIcons()
    {
        var toggleDesktopCommand = new IntPtr(0x7402);
        IntPtr hWnd = IntPtr.Zero;
        if (Environment.OSVersion.Version.Major < 6 || Environment.OSVersion.Version.Minor < 2) //7 and -
            hWnd = GetWindow(FindWindow("Progman", "Program Manager"), GetWindow_Cmd.GW_CHILD);
        else
        {
            var ptrs = FindWindowsWithClass("WorkerW");
            int i = 0;
            while (hWnd == IntPtr.Zero && i < ptrs.Count())
            {
                hWnd = FindWindowEx(ptrs.ElementAt(i), IntPtr.Zero, "SHELLDLL_DefView", null);
                i++;
            }
        }
        SendMessage(hWnd, WM_COMMAND, toggleDesktopCommand, IntPtr.Zero);
    }

Now we can just toggle desktop icons twice:

        ToggleDesktopIcons();
        ToggleDesktopIcons();

Hope this helps someone else ...