C#

public class FileInfo
{
  private int const FILE_ATTRIBUTE_NORMAL = 0x80;

  [DllImport("shell32.dll", CharSet=CharSet.Auto)]
  private static extern IntPtr SHGetFileInfo(
    string path,
    int fileAttributes,
    [MarshalAs(UnmanagedType.Struct), Out]out SHFileInfo info,
    int fileInfoSize,
    [MarshalAs(UnmanagedType.U4)]SHGFI flags);

  [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
  private struct SHFileInfo
  {
    public IntPtr IconHandle;
    public int IconIndex;
    public int Attributes;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=260)]
      public string DisplayName;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=80)]
      public string FileType;
  }

  [Flags]
  private enum SHGFI
  {
    LargeIcon = 0x0,
    SmallIcon = 0x1,
    OpenIcon = 0x2,
    ShallIconSize = 0x4,
    PIDL = 0x08,
    UseFileAttribute = 0x10,
    AddOverlays = 0x20,
    OverlayIndex = 0x40,
    Icon = 0x0100,
    DisplayName = 0x200,
    TypeName = 0x400,
    Attributes = 0x800,
    IconLocation = 0x1000,
    EXEType = 0x2000,
    SysIconIndex = 0x4000,
    LinkOverlay = 0x8000,
    Selected = 0x10000,
    AttrSpecified = 0x20000
  }

  public static bool GetFileInformation(string filename,
    out string fileType, out Image fileImage)
  {
    SHFileInfo info = new SHFileInfo();
    IntPtr retVal = SHGetFileInfo(filename, FILE_ATTRIBUTE_NORMAL,
      out info, Marshal.SizeOf(typeof(SHFileInfo),
      SHGFI.AddOverlays | SHGFI.DisplayName | SHGFI.Icon | SHGFI.SmallIcon
        | SHGFI.TypeName | SHGFI.UseFileAttributes);
    if (retVal != IntPtr.Zero)
    {
      // Set the file type as the user would see it.
      fileType = info.FileType;

      // Get an Image from the Icon, as they're easier to deal with.
      fileImage = Bitmap.FromHicon(info.IconHandle);
      return true;
    }
    else return false;
  }
}

foreach (Control c in this.Controls)
{
  RadioButton rb = c as RadioButton;
  if (rb != null && rb.Checked)
  {
    Console.WriteLine("You selected {0}!", rb.Text);
    break;
  }
}