c# - How to get the PIDL of an open explorer window?

Question

I know how to get all open explorer windows, using Microsoft Internet Controls COM library. From this, I am able to find the LocationURL of those windows. However, this is only set for paths on the file system. Seemingly when virtual objects are displayed, like network printers or the recycle bin, LocationURL is empty. LocationName still seems to be set to the name which is visible on the start bar.

When LocationURL is set, this is sufficient for my purposes to know where the explorer window is pointing to, but how can I find out what it is pointing to for these special folders?

Reading up a bit on pointers to an item identifier list (PIDL). Knowing which PIDL is being shown in the explorer window could identify that. Is there any way to retrieve this?

Answer 1

Here is a sample C# Console app code that gets the PIDL of current Windows explorer windows:

class Program
{
    static void Main(string[] args)
    {
        var shellWindows = new ShellWindows();
        foreach (IWebBrowser2 win in shellWindows)
        {
            IServiceProvider sp = win as IServiceProvider;
            object sb;
            sp.QueryService(SID_STopLevelBrowser, typeof(IShellBrowser).GUID, out sb);
            IShellBrowser shellBrowser = (IShellBrowser)sb;
            object sv;
            shellBrowser.QueryActiveShellView(out sv);
            Console.WriteLine(win.LocationURL + " " + win.LocationName);
            IFolderView fv = sv as IFolderView;
            if (fv != null)
            {
                // only folder implementation support this (IE windows do not for example)
                object pf;
                fv.GetFolder(typeof(IPersistFolder2).GUID, out pf);
                IPersistFolder2 persistFolder = (IPersistFolder2)pf;

                // get folder class, for example
                // CLSID_ShellFSFolder for standard explorer folders
                Guid clsid;
                persistFolder.GetClassID(out clsid);
                Console.WriteLine(" clsid:" + clsid);

                // get current folder pidl
                IntPtr pidl;
                persistFolder.GetCurFolder(out pidl);

                // TODO: do something with pidl

                Marshal.FreeCoTaskMem(pidl); // free pidl's allocated memory
            }
        }
    }

    internal static readonly Guid SID_STopLevelBrowser = new Guid(0x4C96BE40, 0x915C, 0x11CF, 0x99, 0xD3, 0x00, 0xAA, 0x00, 0x4A, 0xE8, 0x37);

    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("6D5140C1-7436-11CE-8034-00AA006009FA")]
    internal interface IServiceProvider
    {
        void QueryService([MarshalAs(UnmanagedType.LPStruct)] Guid guidService, [MarshalAs(UnmanagedType.LPStruct)] Guid riid, [MarshalAs(UnmanagedType.IUnknown)] out object ppvObject);
    }

    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("1AC3D9F0-175C-11d1-95BE-00609797EA4F")]
    internal interface IPersistFolder2
    {
        void GetClassID(out Guid pClassID);
        void Initialize(IntPtr pidl);
        void GetCurFolder(out IntPtr pidl);
    }

    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("000214E2-0000-0000-C000-000000000046")]
    internal interface IShellBrowser
    {
        void _VtblGap0_12(); // skip 12 members
        void QueryActiveShellView([MarshalAs(UnmanagedType.IUnknown)] out object ppshv);
        // the rest is not defined
    }

    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("cde725b0-ccc9-4519-917e-325d72fab4ce")]
    internal interface IFolderView
    {
        void _VtblGap0_2(); // skip 2 members
        void GetFolder([MarshalAs(UnmanagedType.LPStruct)] Guid riid, [MarshalAs(UnmanagedType.IUnknown)] out object ppv);
        // the rest is not defined
    }
}

Note: Shell interfaces are only partially defined as we don't need the full details. Feel free to complete it if you need other information.