如何在.NET中获取文件扩展名的描述

public static string GetFileTypeDescription(string fileNameOrExtension)
    {
        SHFILEINFO shfi;
        if (IntPtr.Zero != SHGetFileInfo(
                            fileNameOrExtension,FILE_ATTRIBUTE_NORMAL,out shfi,(uint)Marshal.SizeOf(typeof(SHFILEINFO)),SHGFI_USEFILEATTRIBUTES | SHGFI_TYPENAME))
        {
            return shfi.szTypeName;
        }
        return null;
    }

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

    [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;
    }

    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

(大多数常量实际上并没有在那段代码中使用,但是无论如何我都会把它们放在你想要根据你的特定需求调整代码的情况下)