How to extract the associated icon of any file in C#.Net

To extract icon of any file, define the below class and the structure:

[StructLayout(LayoutKind.Sequential)]
        public struct SHFILEINFO
        {
            public IntPtr hIcon;
            public IntPtr iIcon;
            public uint dwAttributes;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
            public string szDisplayName;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
            public string szTypeName;
        };


class Win32
        {
            public const uint SHGFI_ICON = 0x100;
            public const uint SHGFI_LARGEICON = 0x0;    // 'Large icon
            public const uint SHGFI_SMALLICON = 0x1;    // 'Small icon

            [DllImport("shell32.dll")]
            public static extern IntPtr SHGetFileInfo(string pszPath,
                                        uint dwFileAttributes,
                                        ref SHFILEINFO psfi,
                                        uint cbSizeFileInfo,
                                        uint uFlags);

            [DllImport("User32.dll")]
            public static extern int DestroyIcon(IntPtr hIcon);
        }

Now define the following function:

SHFILEINFO shinfo = new SHFILEINFO();
/* Define it globally so that you can use the same object for all  the files. */
public Bitmap extractAssociatedIcon(string fName)
        {
            Icon myIcon = null;
            try
            {
                IntPtr hImgSmall;    //the handle to the system image list              

                hImgSmall = Win32.SHGetFileInfo(fName, 0, ref shinfo,
                                 (uint)Marshal.SizeOf(shinfo),
                                  Win32.SHGFI_ICON |
                                  Win32.SHGFI_SMALLICON);

                if (shinfo.hIcon != IntPtr.Zero)
                    myIcon = Icon.FromHandle(shinfo.hIcon);              

            }
            catch (Exception ex)
            {
                // Handle any exception here
            }
            return myIcon.ToBitmap();
        }


Get the icon by calling the above defined function.

Bitmap image = extractAssociatedIcon("fullPath to the file");

Once you get the icon, make sure you destroy the icon. This is very important, else you will run into memory issues.

Win32.DestroyIcon(shinfo.hIcon);