List only devices shown in 'Devices and Printers' panel

Question

I am writing an application in C# that will run on a users PC and I want to list only the devices that are shown in the Windows "Devices and Printers" control panel, things like monitors, keyboard, mouse, speakers etc.

I can use WMI to extract a list of all devices, but is there a way to only extract only those that are shown in that part of control panel rather than the full list?

I have searched online and found nothing relating to this and I can't even find what is the criteria for a device to appear in that list.

Is it possible to access the list of those devices that are shown in that list or, if not, is there a filter that can be applied to the full list that will only show those devices?

thanks in advance

Answer 1

I do it with p/invoke and COM interop by enumerating the shell items in Microsoft.DevicesAndPrinters and filtering by making sure that PKEY_Devices_CategoryIds contains an item starting with PrintFax.

There's no way to boil the necessary interop definitions down to fit in an answer, but this is the logic I use to enumerate the display name, the DEVMODE name, and images of any size:

public sealed class PrinterInfo
{
    public string IdName { get; }
    public string DisplayName { get; }
    public Bitmap Image { get; }

    private PrinterInfo(string idName, string displayName, Bitmap image)
    {
        IdName = idName;
        DisplayName = displayName;
        Image = image;
    }

    public static IReadOnlyList<PrinterInfo> GetInstalledPrinterNamesAndImages(Size imageSize)
    {
        var r = new List<PrinterInfo>();

        using (var folderIdList = CreateDevicesAndPrintersIDL())
        {
            var folder = GetShellFolder(folderIdList);
            var enumerator = folder.EnumObjects(IntPtr.Zero, SHCONTF.NONFOLDERS);

            for (;;)
            {
                // If you request more than are left, actualCount is 0, so we'll do one at a time.
                var next = enumerator.Next(1, out var relativeIdList, out var actualCount);
                next.ThrowIfError();
                if (next == HResult.False || actualCount != 1) break; // printerChild is junk

                using (relativeIdList)
                using (var absoluteIdList = ILCombine(folderIdList, relativeIdList))
                {
                    var shellItem = GetShellItem(absoluteIdList);
                    var idName = GetPrinterFriendlyNameIfPrinter(shellItem);
                    if (idName != null)
                        r.Add(new PrinterInfo(idName, GetDisplayName(shellItem), GetImage(shellItem, imageSize)));
                }
            }
        }

        return r;
    }

    private static ItemIdListSafeHandle CreateDevicesAndPrintersIDL()
    {
        SHGetKnownFolderIDList(FOLDERID.ControlPanelFolder, KF_FLAG.DEFAULT, IntPtr.Zero, out var controlPanelIdList).ThrowIfError();
        using (controlPanelIdList)
        {
            GetShellFolder(controlPanelIdList).ParseDisplayName(IntPtr.Zero, null, "::{A8A91A66-3A7D-4424-8D24-04E180695C7A}", IntPtr.Zero, out var childDevicesAndPriversIdList, IntPtr.Zero);
            using (childDevicesAndPriversIdList)
                return ILCombine(controlPanelIdList, childDevicesAndPriversIdList);
        }
    }

    private static string GetPrinterFriendlyNameIfPrinter(IShellItem2 shellItem)
    {
        // Devices_PrimaryCategory returns "Printers" for printers and faxes on Windows 10 but "Printers and faxes" on Windows 7.
        using (var categoryIds = new PropVariantSafeHandle())
        {
            shellItem.GetProperty(PKEY.Devices_CategoryIds, categoryIds).ThrowIfError();
            if (!categoryIds.ToStringVector().Any(id => id.StartsWith("PrintFax", StringComparison.OrdinalIgnoreCase)))
                return null;
        }

        // The canonical or "friendly name" needed to match the devmode
        // https://blogs.msdn.microsoft.com/asklar/2009/10/21/getting-the-printer-friendly-name-from-the-device-center-shell-folder/
        // PKEY_Devices_InterfacePaths doesn't seem to ever be found, but PKEY_Devices_FriendlyName works so...
        shellItem.GetString(PKEY.Devices_FriendlyName, out var friendlyName).ThrowIfError();
        return friendlyName.ReadAndFree();
    }

    private static string GetDisplayName(IShellItem2 shellItem)
    {
        return shellItem.GetDisplayName(SIGDN.NORMALDISPLAY).ReadAndFree();
    }

    private static Bitmap GetImage(IShellItem2 shellItem, Size imageSize)
    {
        return ((IShellItemImageFactory)shellItem).GetImage(new POINT(imageSize.Width, imageSize.Height), SIIGBF.SIIGBF_BIGGERSIZEOK)
            .CopyAndFree(); // Bitmap.FromHbitmap is useless with alpha, so make a copy
    }


    private static IShellFolder GetShellFolder(ItemIdListSafeHandle itemIdList)
    {
        SHBindToObject(IntPtr.Zero, itemIdList, null, typeof(IShellFolder).GUID, out var objShellFolder).ThrowIfError();
        return (IShellFolder)objShellFolder;
    }

    private static IShellItem2 GetShellItem(ItemIdListSafeHandle itemIdList)
    {
        SHCreateItemFromIDList(itemIdList, typeof(IShellItem2).GUID, out var objShellItem).ThrowIfError();
        return (IShellItem2)objShellItem;
    }
}

(C# 7)

Here's a full demo you can compile: https://github.com/jnm2/example-devices-and-printers/tree/master/src

For a C# 6 version which doesn't require ValueTuple, see https://github.com/jnm2/example-devices-and-printers/tree/master/src-csharp6.

I'm happy to answer any questions.