GifImage

    public class GifImage : Image
    {
        GifBitmapDecoder _gf;
        Int32Animation _anim;
        bool _animationIsWorking = false;

        public Uri Uri
        {
            set
            {
                _gf = new GifBitmapDecoder(value, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
                _anim = new Int32Animation(0, _gf.Frames.Count - 1, new Duration(new TimeSpan(0, 0, 0, _gf.Frames.Count / 10, (int)((_gf.Frames.Count / 10.0 - _gf.Frames.Count / 10) * 1000))));
                _anim.RepeatBehavior = RepeatBehavior.Forever;
                Source = _gf.Frames[0]; ;
            }
        }

        public int FrameIndex
        {
            get { return (int)GetValue(FrameIndexProperty); }
            set { SetValue(FrameIndexProperty, value); }
        }

        public static readonly DependencyProperty FrameIndexProperty =
            DependencyProperty.Register("FrameIndex", typeof(int), typeof(GifImage), new UIPropertyMetadata(0, new PropertyChangedCallback(ChangingFrameIndex)));

        static void ChangingFrameIndex(DependencyObject obj, DependencyPropertyChangedEventArgs ev)
        {
            var ob = obj as GifImage;
            ob.Source = ob._gf.Frames[(int)ev.NewValue];
            ob.InvalidateVisual();
        }

        protected override void OnRender(DrawingContext dc)
        {
            base.OnRender(dc);

            if (_animationIsWorking) return;

            BeginAnimation(FrameIndexProperty, _anim);
            _animationIsWorking = true;
        }
    }