Get File Icon used by Shell

Question

In .Net (C# or VB: don't care), given a file path string, FileInfo struct, or FileSystemInfo struct for a real existing file, how can I determine the icon(s) used by the shell (explorer) for that file?

I'm not currently planning to use this for anything, but I became curious about how to do it when looking at this question and I thought it would be useful to have archived here on SO.

Answer 1

This works for me in my projects, hope this helps someone.

It's C# with P/Invokes it will work so far on x86/x64 systems since WinXP.

(Shell.cs)

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

namespace IconExtraction
{
    internal sealed class Shell : NativeMethods
    {
        #region OfExtension

        ///<summary>
        /// Get the icon of an extension
        ///</summary>
        ///<param name="filename">filename</param>
        ///<param name="overlay">bool symlink overlay</param>
        ///<returns>Icon</returns>
        public static Icon OfExtension(string filename, bool overlay = false)
        {
            string filepath;
            string[] extension = filename.Split('.');
            string dirpath = Path.Combine(System.AppDomain.CurrentDomain.BaseDirectory, "cache");
            Directory.CreateDirectory(dirpath);
            if (String.IsNullOrEmpty(filename) || extension.Length == 1)
            {
                filepath = Path.Combine(dirpath, "dummy_file");
            }
            else
            {
                filepath = Path.Combine(dirpath, String.Join(".", "dummy", extension[extension.Length - 1]));
            }
            if (File.Exists(filepath) == false)
            {
                File.Create(filepath);
            }
            Icon icon = OfPath(filepath, true, true, overlay);
            return icon;
        }
        #endregion

        #region OfFolder

        ///<summary>
        /// Get the icon of an extension
        ///</summary>
        ///<returns>Icon</returns>
        ///<param name="overlay">bool symlink overlay</param>
        public static Icon OfFolder(bool overlay = false)
        {
            string dirpath = Path.Combine(System.AppDomain.CurrentDomain.BaseDirectory, "cache", "dummy");
            Directory.CreateDirectory(dirpath);
            Icon icon = OfPath(dirpath, true, true, overlay);
            return icon;
        }
        #endregion

        #region OfPath

        ///<summary>
        /// Get the normal,small assigned icon of the given path
        ///</summary>
        ///<param name="filepath">physical path</param>
        ///<param name="small">bool small icon</param>
        ///<param name="checkdisk">bool fileicon</param>
        ///<param name="overlay">bool symlink overlay</param>
        ///<returns>Icon</returns>
        public static Icon OfPath(string filepath, bool small = true, bool checkdisk = true, bool overlay = false)
        {
            Icon clone;
            SHGFI_Flag flags;
            SHFILEINFO shinfo = new SHFILEINFO();
            if (small)
            {
                flags = SHGFI_Flag.SHGFI_ICON | SHGFI_Flag.SHGFI_SMALLICON;
            }
            else
            {
                flags = SHGFI_Flag.SHGFI_ICON | SHGFI_Flag.SHGFI_LARGEICON;
            }
            if (checkdisk == false)
            {
                flags |= SHGFI_Flag.SHGFI_USEFILEATTRIBUTES;
            }
            if (overlay)
            {
                flags |= SHGFI_Flag.SHGFI_LINKOVERLAY;
            }
            if (SHGetFileInfo(filepath, 0, ref shinfo, Marshal.SizeOf(shinfo), flags) == 0)
            {
                throw (new FileNotFoundException());
            }
            Icon tmp = Icon.FromHandle(shinfo.hIcon);
            clone = (Icon)tmp.Clone();
            tmp.Dispose();
            if (DestroyIcon(shinfo.hIcon) != 0)
            {
                return clone;
            }
            return clone;
        }
        #endregion
    }
}

(NativeMethods.cs)

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

namespace IconExtraction
{
    internal class NativeMethods
    {
        public 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("user32.dll")]
        public static extern int DestroyIcon(IntPtr hIcon);

        [DllImport("shell32.dll", CharSet = CharSet.Auto, BestFitMapping = false, ThrowOnUnmappableChar = true)]
        public static extern IntPtr ExtractIcon(IntPtr hInst, string lpszExeFileName, int nIconIndex);

        [DllImport("Shell32.dll", BestFitMapping = false, ThrowOnUnmappableChar = true)]
        public static extern int SHGetFileInfo(string pszPath, int dwFileAttributes, ref SHFILEINFO psfi, int cbFileInfo, SHGFI_Flag uFlags);

        [DllImport("Shell32.dll")]
        public static extern int SHGetFileInfo(IntPtr pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, int cbFileInfo, SHGFI_Flag uFlags);
    }

    public enum SHGFI_Flag : uint
    {
        SHGFI_ATTR_SPECIFIED = 0x000020000,
        SHGFI_OPENICON = 0x000000002,
        SHGFI_USEFILEATTRIBUTES = 0x000000010,
        SHGFI_ADDOVERLAYS = 0x000000020,
        SHGFI_DISPLAYNAME = 0x000000200,
        SHGFI_EXETYPE = 0x000002000,
        SHGFI_ICON = 0x000000100,
        SHGFI_ICONLOCATION = 0x000001000,
        SHGFI_LARGEICON = 0x000000000,
        SHGFI_SMALLICON = 0x000000001,
        SHGFI_SHELLICONSIZE = 0x000000004,
        SHGFI_LINKOVERLAY = 0x000008000,
        SHGFI_SYSICONINDEX = 0x000004000,
        SHGFI_TYPENAME = 0x000000400
    }
}

Answer 2

This link seems to have some info. It involves a lot of registry traversing, but it seems doable. The examples are in C++

Answer 3

• determine extension
• in registry, go to "HKCR\.{extension}", read the default value (let's call it filetype)
• in "HKCR\{filetype}\DefaultIcon", read the default value: this is the path to the icon file (or icon container file, like an .exe with an embedded icon resource)
• if needed, use your preferred method of extracting the icon resource out of the mentioned file

edit/moved up from the comments:

If the icon is in a container file (this is quite common), there will be a counter after the path, like this: "foo.exe,3". This means it is icon number 4 (the index is zero-based) of the available icons. A value of ",0" is implicit (and optional). If the counter is 0 or missing, the fist available icon will be used by the shell.