SHGetFileInfo：设置SHGFI_OPENICON没有任何影响

Question

我有一个TreeView用于表示我的文件系统，并使用SHGetFileInfo函数显示树的每个路径的系统图标。我正在尝试在扩展TreeViewItem时将文件夹图标更改为打开的文件夹图标。但是，启用此功能似乎没有任何影响，无论是否设置SHGFI_OPENICON，图标都是相同的。

这不是绑定问题，因为硬编码总是使用SHGFI_OPENICON具有相同的结果。

这是我正在使用的转换器。

public class GetSystemIconConvertor : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        string path = values[0].ToString();
        bool isExpanded = (bool)values[1];
        return GetIcon(path, isExpanded);
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    public static ImageSource GetIcon(string path, bool _isOpen)
    {
        uint flags = SHGFI_ICON | SHGFI_USEFILEATTRIBUTES | SHGFI_SMALLICON;
        if (_isOpen)
            flags |= SHGFI_OPENICON;

        uint attributes = FILE_ATTRIBUTE_NORMAL;
        if ((File.GetAttributes(path) & FileAttributes.Directory) == FileAttributes.Directory)
            attributes |= FILE_ATTRIBUTE_DIRECTORY;

        SHFILEINFO shfi;
        if (SHGetFileInfo(path, attributes, out shfi, (uint)Marshal.SizeOf(typeof(SHFILEINFO)), flags) != 0)
        {
            return System.Windows.Interop.Imaging.CreateBitmapSourceFromHIcon(shfi.hIcon, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
        }
        return null;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct SHFILEINFO
    {
        public IntPtr hIcon;
        public int iIcon;
        public uint dwAttributes;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
        public string szDisplayName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
        public string szTypeName;
    }

    [DllImport("shell32")]
    private static extern int SHGetFileInfo(string pszPath, uint dwFileAttributes, out SHFILEINFO psfi, uint cbFileInfo, uint flags);

    const uint FILE_ATTRIBUTE_READONLY = 0x00000001;
    const uint FILE_ATTRIBUTE_HIDDEN = 0x00000002;
    const uint FILE_ATTRIBUTE_SYSTEM = 0x00000004;
    const uint FILE_ATTRIBUTE_DIRECTORY = 0x00000010;
    const uint FILE_ATTRIBUTE_ARCHIVE = 0x00000020;
    const uint FILE_ATTRIBUTE_DEVICE = 0x00000040;
    const uint FILE_ATTRIBUTE_NORMAL = 0x00000080;
    const uint FILE_ATTRIBUTE_TEMPORARY = 0x00000100;
    const uint FILE_ATTRIBUTE_SPARSE_FILE = 0x00000200;
    const uint FILE_ATTRIBUTE_REPARSE_POINT = 0x00000400;
    const uint FILE_ATTRIBUTE_COMPRESSED = 0x00000800;
    const uint FILE_ATTRIBUTE_OFFLINE = 0x00001000;
    const uint FILE_ATTRIBUTE_NOT_CONTENT_INDEXED = 0x00002000;
    const uint FILE_ATTRIBUTE_ENCRYPTED = 0x00004000;
    const uint FILE_ATTRIBUTE_VIRTUAL = 0x00010000;

    const uint SHGFI_ICON = 0x000000100;     // get icon
    const uint SHGFI_DISPLAYNAME = 0x000000200;     // get display name
    const uint SHGFI_TYPENAME = 0x000000400;     // get type name
    const uint SHGFI_ATTRIBUTES = 0x000000800;     // get attributes
    const uint SHGFI_ICONLOCATION = 0x000001000;     // get icon location
    const uint SHGFI_EXETYPE = 0x000002000;     // return exe type
    const uint SHGFI_SYSICONINDEX = 0x000004000;     // get system icon index
    const uint SHGFI_LINKOVERLAY = 0x000008000;     // put a link overlay on icon
    const uint SHGFI_SELECTED = 0x000010000;     // show icon in selected state
    const uint SHGFI_ATTR_SPECIFIED = 0x000020000;     // get only specified attributes
    const uint SHGFI_LARGEICON = 0x000000000;     // get large icon
    const uint SHGFI_SMALLICON = 0x000000001;     // get small icon
    const uint SHGFI_OPENICON = 0x000000002;     // get open icon
    const uint SHGFI_SHELLICONSIZE = 0x000000004;     // get shell size icon
    const uint SHGFI_PIDL = 0x000000008;     // pszPath is a pidl
    const uint SHGFI_USEFILEATTRIBUTES = 0x000000010;     // use passed dwFileAttribute
}