Xamarin.iOS でジェスチャを認識する ref: http://qiita.com/amay077/items/a6754176f2abe339adce

GesturesSample_ViewDidLoad.cs

// Tap gesture
this.View.AddGestureRecognizer(new UITapGestureRecognizer(tap => 
{
    Debug.WriteLine("Double Tap.");
}) 
{ 
    NumberOfTapsRequired = 2 // Double tap 
});

// Drag(Pan) gesture
this.View.AddGestureRecognizer(new UIPanGestureRecognizer(pan => 
{
    var p = pan.TranslationInView(this.View);
    var v = pan.VelocityInView(this.View);
    Debug.WriteLine("Pan. transration:{0}, velocity:{1}", p, v);
}));

// Pinch gesture
this.View.AddGestureRecognizer(new UIPinchGestureRecognizer(pin => 
{
    var scale = pin.Scale;
    var v = pin.Velocity;
    Debug.WriteLine("Pinch. scale:{0}, velocity:{1}", scale, v);
}));

// Swipe gesture
this.View.AddGestureRecognizer(new UISwipeGestureRecognizer(sw => 
{
    Debug.WriteLine("Swipe.");
}));

// Rotate gesture
this.View.AddGestureRecognizer(new UIRotationGestureRecognizer(ro => 
{
    var rotation = ro.Rotation;
    var v = ro.Velocity;
    Debug.WriteLine("Rotate. rotation:{0}, velocity:{1}", rotation, v);
}));

// Long press gesture
this.View.AddGestureRecognizer(new UILongPressGestureRecognizer(lp => 
{
    Debug.WriteLine("Long press.");
}));