资料：http://d.download.csdn.net/down/173795/ucxxg

http://www.xker.com/page/e2007/0116/13279.html

    public class FileIcon
    {
        /// <summary>
        ///  Get default icon from file
        /// </summary>
        /// <param name="fileName">File name
        /// </param>
        /// <param name="largeIcon">Large icon or not</param>
        /// <returns>default icon</returns>
        public static Icon GetFileIcon(string fileName, bool largeIcon)
        {

            SHFILEINFO info = new SHFILEINFO(true);
            int cbFileInfo = Marshal.SizeOf(info);
            SHGFI flags;
            if (largeIcon)
                flags = SHGFI.Icon | SHGFI.LargeIcon | SHGFI.UseFileAttributes;
            else
                flags = SHGFI.Icon | SHGFI.SmallIcon | SHGFI.UseFileAttributes;

            SHGetFileInfo(fileName, 256, out info, (uint)cbFileInfo, flags);
            return Icon.FromHandle(info.hIcon);
        }


        [DllImport("Shell32.dll")]
        private static extern int SHGetFileInfo
          (
          string pszPath,
          uint dwFileAttributes,
          out   SHFILEINFO psfi,
          uint cbfileInfo,
          SHGFI uFlags
          );

        [StructLayout(LayoutKind.Sequential)]
        private struct SHFILEINFO
        {
            public SHFILEINFO(bool b)
            {
                hIcon = IntPtr.Zero; iIcon = 0; dwAttributes = 0; szDisplayName = ""; szTypeName = "";
            }
            public IntPtr hIcon;
            public int iIcon;
            public uint dwAttributes;
            [MarshalAs(UnmanagedType.LPStr, SizeConst = 260)]
            public string szDisplayName;
            [MarshalAs(UnmanagedType.LPStr, SizeConst = 80)]
            public string szTypeName;
        };

        private enum SHGFI
        {
            SmallIcon = 0x00000001,
            LargeIcon = 0x00000000,
            Icon = 0x00000100,
            DisplayName = 0x00000200,
            Typename = 0x00000400,
            SysIconIndex = 0x00004000,
            UseFileAttributes = 0x00000010
        }
    }

刚才看了一下，Astar给的内容已经很全了