public static void Main()
{
    var frameList = Gif.LoadAnimatedGif ("b.gif");

    var i = 0;
    foreach(var frame in frameList)
        frame.Image.Save ("frame_" + i++ + ".png");
}
public class Gif
{
    public static List<Frame> LoadAnimatedGif(string path)
    {
        //If path is not found, we should throw an IO exception
        if (!File.Exists(path))
            throw new IOException("File does not exist");

        //Load the image
        var img = Image.FromFile(path);

        //Count the frames
        var frameCount = img.GetFrameCount(FrameDimension.Time);

        //If the image is not an animated gif, we should throw an
        //argument exception
        if (frameCount <= 1)
            throw new ArgumentException("Image is not animated");

        //List that will hold all the frames
        var frames = new List<Frame>();

        //Get the times stored in the gif
        //PropertyTagFrameDelay ((PROPID) 0x5100) comes from gdiplusimaging.h
        //More info on http://msdn.microsoft.com/en-us/library/windows/desktop/ms534416(v=vs.85).aspx
        var times = img.GetPropertyItem(0x5100).Value;

        //Convert the 4bit duration chunk into an int

        for (int i = 0; i < frameCount; i++)
        {
            //convert 4 bit value to integer
            var duration = BitConverter.ToInt32(times, 4*i);

            //Add a new frame to our list of frames
            frames.Add(
                new Frame()
                {
                Image = new Bitmap(img),
                Duration = duration
            });

            //Set the write frame before we save it
            img.SelectActiveFrame(FrameDimension.Time, i);


        }

        //Dispose the image when we're done
        img.Dispose();

        return frames;
    }
}

//Class to store each frame
public class Frame
{
    public Bitmap Image { get; set; }
    public int Duration { get; set;}
}