如何在C#中获取常见的文件类型图标？

using System;
using System.Drawing;
using System.Runtime.InteropServices;

public class FileIcon
{
    [DllImport("shell32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, uint cbSizeFileInfo, uint uFlags);

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    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 SHGFI_ICON = 0x100;
    private const uint SHGFI_LARGEICON = 0x0;
    private const uint SHGFI_SMALLICON = 0x1;

    public static Icon GetFileIcon(string fileName, bool largeIcon)
    {
        SHFILEINFO shfi = new SHFILEINFO();
        uint flags = SHGFI_ICON | (largeIcon ? SHGFI_LARGEICON : SHGFI_SMALLICON);
        SHGetFileInfo(fileName, 0, ref shfi, (uint)Marshal.SizeOf(shfi), flags);
        return Icon.FromHandle(shfi.hIcon);
    }
}

Icon icon = FileIcon.GetFileIcon("C:\\example.txt", true);