Get program icons

I'm making a explorer like app to browse files stored on my computer. My app will be in "Icon" view. The q开发者_如何学运维uestion is: How to display the icon of an exe file?

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There are several ways to do that. The easiest is probably to add a reference to System.Drawing and take advantage of the Icon.ExtractAssociatedIcon method:

public static ImageSource GetIcon(string fileName)
{
    Icon icon = Icon.ExtractAssociatedIcon(fileName);
    return System.Windows.Interop.Imaging.CreateBitmapSourceFromHIcon(
                icon.Handle, 
                new Int32Rect(icon.Width, icon.Height),
                BitmapSizeOptions.FromEmptyOptions());
}

Another option, if you don't want to use System.Drawing, is to obtain the icon from the SHGetFileInfo API. It's more difficult, but also much more flexible; for instance you can get the icon of a file that doesn't exist, based on the extension (of course for an executable it's not very useful, since it would return the default icon for executable files).

public static ImageSource GetIcon(string path, bool smallIcon, bool isDirectory)
{
    // SHGFI_USEFILEATTRIBUTES takes the file name and attributes into account if it doesn't exist
    uint flags = SHGFI_ICON | SHGFI_USEFILEATTRIBUTES;
    if (smallIcon)
        flags |= SHGFI_SMALLICON;

    uint attributes = FILE_ATTRIBUTE_NORMAL;
    if (isDirectory)
        attributes |= FILE_ATTRIBUTE_DIRECTORY;

    SHFILEINFO shfi;
    if (0 != SHGetFileInfo(
                path,
                attributes,
                out shfi,
                (uint)Marshal.SizeOf(typeof(SHFILEINFO)),
                flags))
    {
        return System.Windows.Interop.Imaging.CreateBitmapSourceFromHIcon(
                    shfi.hIcon, 
                    Int32Rect.Empty,
                    BitmapSizeOptions.FromEmptyOptions());
    }
    return null;
}

[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;
}

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

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

Another advantage of this approach is that it can also get the icon for a directory (see last edit in the code), which isn't possible with Icon.ExtractAssociatedIcon