C#のWPFでEXEファイルのアイコンを抽出するコード

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0-windows</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <UseWPF>true</UseWPF>
  </PropertyGroup>

</Project>

using System.IO;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Media.Imaging;

internal static class Program
{
    [STAThread]
    private static void Main(string[] args)
    {
        // 取得対象: notepad.exe
        string exePath = Environment.ExpandEnvironmentVariables(@"%SystemRoot%\system32\notepad.exe");
        if (!File.Exists(exePath))
        {
            Console.Error.WriteLine("notepad.exe が見つかりません: " + exePath);
            return;
        }

        // まずは 256px(Jumbo) を狙い、ダメなら順次縮小、最後に ExtractIcon でフォールバック
        BitmapSource? icon = GetShellIcon(exePath, 256)
                          ?? GetShellIcon(exePath, 48)
                          ?? GetIconViaExtractIcon(exePath);

        if (icon == null)
        {
            Console.Error.WriteLine("アイコン取得に失敗しました。");
            return;
        }

        // PNG保存
        string outPath = Path.GetFullPath("notepad_icon_256.png");
        using (var fs = File.Create(outPath))
        {
            var enc = new PngBitmapEncoder();
            enc.Frames.Add(BitmapFrame.Create(icon));
            enc.Save(fs);
        }

        Console.WriteLine("Saved: " + outPath);
    }

    private enum SHIL : int { Small = 0, Large = 1, ExtraLarge = 2, SysSmall = 3, Jumbo = 4 }

    [ComImport, Guid("46EB5926-582E-4017-9FDF-E8998DAA0950"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface IImageList
    {
        // 必要なのは GetIcon だけ
        [PreserveSig] int Add(IntPtr hbmImage, IntPtr hbmMask, ref int pi);
        [PreserveSig] int ReplaceIcon(int i, IntPtr hicon, ref int pi);
        [PreserveSig] int SetOverlayImage(int iImage, int iOverlay);
        [PreserveSig] int Replace(int i, IntPtr hbmImage, IntPtr hbmMask);
        [PreserveSig] int AddMasked(IntPtr hbmImage, int crMask, ref int pi);
        [PreserveSig] int Draw(ref IMAGELISTDRAWPARAMS pimldp);
        [PreserveSig] int Remove(int i);
        [PreserveSig] int GetIcon(int i, int flags, out IntPtr picon);
        // 以降のメソッドは今回未使用
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct IMAGELISTDRAWPARAMS
    {
        public int cbSize;
        public IntPtr himl;
        public int i;
        public IntPtr hdcDst;
        public int x;
        public int y;
        public int cx;
        public int cy;
        public int xBitmap; // 未使用
        public int yBitmap; // 未使用
        public int rgbBk;
        public int rgbFg;
        public int fStyle;
        public int dwRop;
        public int fState;
        public int Frame;
        public int crEffect;
    }

    [DllImport("shell32.dll", EntryPoint = "#727")]
    private static extern int SHGetImageList(int iImageList, ref Guid riid, out IImageList ppv);

    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
    private static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, out SHFILEINFO psfi, uint cbFileInfo, uint uFlags);

    [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;
    }

    private const uint SHGFI_ICON = 0x000000100;
    private const uint SHGFI_LARGEICON = 0x000000000;
    private const uint SHGFI_SYSICONINDEX = 0x000004000;
    private const int  ILD_TRANSPARENT = 0x00000001;

    private static BitmapSource? GetShellIcon(string exePath, int size)
    {
        // 1) システムイメージリスト上のインデックスを取得
        var shfi = new SHFILEINFO();
        SHGetFileInfo(exePath, 0, out shfi, (uint)Marshal.SizeOf<SHFILEINFO>(),
                      SHGFI_SYSICONINDEX | SHGFI_ICON | SHGFI_LARGEICON);
        int index = shfi.iIcon;

        // 2) 目的サイズに応じたリストを選択
        SHIL list = size >= 256 ? SHIL.Jumbo
                  : size >= 48  ? SHIL.ExtraLarge
                  : size >= 32  ? SHIL.Large
                  : SHIL.Small;

        Guid iidImageList = typeof(IImageList).GUID;
        if (SHGetImageList((int)list, ref iidImageList, out var imgList) != 0)
            return null;

        // 3) 取り出し
        IntPtr hIcon = IntPtr.Zero;
        int hr = imgList.GetIcon(index, ILD_TRANSPARENT, out hIcon);
        if (hr != 0 || hIcon == IntPtr.Zero) return null;

        try
        {
            var bmp = Imaging.CreateBitmapSourceFromHIcon(
                hIcon,
                Int32Rect.Empty,
                BitmapSizeOptions.FromWidthAndHeight(size, size));
            bmp.Freeze();
            return bmp;
        }
        finally
        {
            DestroyIcon(hIcon);
            if (shfi.hIcon != IntPtr.Zero) DestroyIcon(shfi.hIcon);
        }
    }

    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
    private static extern IntPtr ExtractIcon(IntPtr hInst, string lpszExeFileName, int nIconIndex);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool DestroyIcon(IntPtr hIcon);

    private static BitmapSource? GetIconViaExtractIcon(string exePath)
    {
        IntPtr hIcon = ExtractIcon(IntPtr.Zero, exePath, 0);
        if (hIcon == IntPtr.Zero)
            return null;

        try
        {
            var bmp = Imaging.CreateBitmapSourceFromHIcon(
                hIcon,
                Int32Rect.Empty,
                BitmapSizeOptions.FromEmptyOptions());
            bmp.Freeze();
            return bmp;
        }
        finally
        {
            DestroyIcon(hIcon);
        }
    }
}