C#

// define a struct for getting info from shell

[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;
};

// define this class for invoking shell api to get file information
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);
}

// write the following code where you want to get the selected file icon.

IntPtr hImgSmall; //the handle to the system image list
string fName = "c:\\getfileicon.cs"; //  'the file name to get icon from
SHFILEINFO shinfo = new SHFILEINFO();

//Use this to get the small Icon
hImgSmall = Win32.SHGetFileInfo(fName, 0, ref shinfo,(uint)Marshal.SizeOf(shinfo),Win32.SHGFI_ICON |Win32.SHGFI_SMALLICON);

/*
	//Use this to get the small Icon
	hImgLarge = Win32.SHGetFileInfo(fName, 0, ref shinfo,(uint)Marshal.SizeOf(shinfo),Win32.SHGFI_ICON |Win32.SHGFI_LARGEICON); 
*/

//The icon is returned in the hIcon member of the shinfo struct
System.Drawing.Icon myIcon = System.Drawing.Icon.FromHandle(shinfo.hIcon);

// do whatever with this icon. i.e I am adding it to an Image List.
imageList1.Images.Add(myIcon);