Question

我正在用C＃编写一个可在用户PC上运行的应用程序，我只想列出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提取所有设备的列表，但是有没有办法只提取那些显示在控制面板部分而不是完整列表中的那些？

我在网上搜索过，发现与此无关，我甚至无法找到设备在该列表中出现的条件。

是否可以访问该列表中显示的那些设备的列表，如果没有，是否有可以应用于仅显示这些设备的完整列表的过滤器？

提前致谢

Answer 1

我通过枚举Microsoft.DevicesAndPrinters中的shell项并通过确保PKEY_Devices_CategoryIds包含以PrintFax开头的项目进行过滤来实现p / invoke和COM interop。

没有办法将必要的互操作定义简化为适合答案，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）

这是一个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。

仅列出“设备和打印机”面板中显示的设备

1 个答案: