文件类型返回空字符串

Question

我正在尝试使用c＃获取文件类型名称（例如文件夹，位图图像，文本文件等）。

由于特权原因，我不想从注册表中获取信息。

我从互联网上找到了这种方法。

它对于获取文件图标（SHGFI_LARGEICON，SHGFI_SMALLICON）效果很好

但是此方法始终返回空白 szTypeName 。

我尝试了不同的组合，但相同。

我的系统是Windows 10 EE

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

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

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
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.dll")]
private static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, out SHFILEINFO psfi, uint cbFileInfo, uint flags);


public static string GetFileTypeDescription(string fileNameOrExtension)
{
    SHFILEINFO shfi;
    //string ext = Path.GetExtension(fileNameOrExtension);
    //string path = Path.GetTempPath();
    //fileNameOrExtension = Path.Combine(path, "Dumdumdumedumedum." + ext);
    //File.Create(fileNameOrExtension).Dispose();
    if (IntPtr.Zero != SHGetFileInfo(
                        fileNameOrExtension,
                        FILE_ATTRIBUTE_NORMAL,
                        out shfi,
                        (uint)Marshal.SizeOf(typeof(SHFILEINFO)),
                        SHGFI_USEFILEATTRIBUTES | SHGFI_TYPENAME))
    {
        return shfi.szTypeName;
    }
    return null;
}