仅列出'Devices and Printers‘面板中显示的设备

Question

我正在用C#编写一个应用程序，它将在用户的PC上运行，我想只列出Windows“设备和打印机”控制面板中显示的设备，如显示器、键盘、鼠标、扬声器等。

我可以使用WMI来提取所有设备的列表，但是有没有一种方法可以只提取在控制面板的该部分中显示的设备，而不是整个列表？

我在网上搜索过，没有发现任何与此相关的内容，我甚至找不到设备出现在该列表中的标准。

是否可以访问该列表中显示的设备列表，如果不能，是否有可应用于仅显示这些设备的完整列表的过滤器？

提前感谢

Answer 1

我使用p/invoke和COM interop来实现这一点，方法是枚举Microsoft.DevicesAndPrinters中的外壳项，并确保PKEY_Devices_CategoryIds包含以PrintFax开头的项进行过滤。

没有办法将必要的互操作定义归结为一个答案，但这是我用来枚举显示名称、DEVMODE名称和任何大小的图像的逻辑：

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)

下面是您可以编译的完整演示：https://github.com/jnm2/example-devices-and-printers/tree/master/src

对于不需要ValueTuple的C# 6版本，请参阅https://github.com/jnm2/example-devices-and-printers/tree/master/src-csharp6。

我很乐意回答任何问题。