1 files changed, 91 insertions, 0 deletions
diff --git a/Xamarin.Forms.Core/Interactivity/EventTrigger.cs b/Xamarin.Forms.Core/Interactivity/EventTrigger.cs
new file mode 100644
index 00000000..52e221a0
--- /dev/null
+++ b/Xamarin.Forms.Core/Interactivity/EventTrigger.cs
@@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+
+namespace Xamarin.Forms
+{
+	[ContentProperty("Actions")]
+	public sealed class EventTrigger : TriggerBase
+	{
+		static readonly MethodInfo s_handlerinfo = typeof(EventTrigger).GetRuntimeMethods().Single(mi => mi.Name == "OnEventTriggered" && mi.IsPublic == false);
+		readonly List<BindableObject> _associatedObjects = new List<BindableObject>();
+
+		EventInfo _eventinfo;
+
+		string _eventname;
+		Delegate _handlerdelegate;
+
+		public EventTrigger() : base(typeof(BindableObject))
+		{
+			Actions = new SealedList<TriggerAction>();
+		}
+
+		public IList<TriggerAction> Actions { get; }
+
+		public string Event
+		{
+			get { return _eventname; }
+			set
+			{
+				if (_eventname == value)
+					return;
+				if (IsSealed)
+					throw new InvalidOperationException("Event cannot be changed once the Trigger has been applied");
+				OnPropertyChanging();
+				_eventname = value;
+				OnPropertyChanged();
+			}
+		}
+
+		internal override void OnAttachedTo(BindableObject bindable)
+		{
+			base.OnAttachedTo(bindable);
+			if (!string.IsNullOrEmpty(Event))
+				AttachHandlerTo(bindable);
+			_associatedObjects.Add(bindable);
+		}
+
+		internal override void OnDetachingFrom(BindableObject bindable)
+		{
+			_associatedObjects.Remove(bindable);
+			DetachHandlerFrom(bindable);
+			base.OnDetachingFrom(bindable);
+		}
+
+		internal override void OnSeal()
+		{
+			base.OnSeal();
+			((SealedList<TriggerAction>)Actions).IsReadOnly = true;
+		}
+
+		void AttachHandlerTo(BindableObject bindable)
+		{
+			try
+			{
+				_eventinfo = bindable.GetType().GetRuntimeEvent(Event);
+				_handlerdelegate = s_handlerinfo.CreateDelegate(_eventinfo.EventHandlerType, this);
+			}
+			catch (Exception)
+			{
+				Log.Warning("EventTrigger", "Can not attach EventTrigger to {0}.{1}. Check if the handler exists and if the signature is right.", bindable.GetType(), Event);
+			}
+			if (_eventinfo != null && _handlerdelegate != null)
+				_eventinfo.AddEventHandler(bindable, _handlerdelegate);
+		}
+
+		void DetachHandlerFrom(BindableObject bindable)
+		{
+			if (_eventinfo != null && _handlerdelegate != null)
+				_eventinfo.RemoveEventHandler(bindable, _handlerdelegate);
+		}
+
+		[Preserve]
+		void OnEventTriggered(object sender, EventArgs e)
+		{
+			var bindable = (BindableObject)sender;
+			foreach (TriggerAction action in Actions)
+				action.DoInvoke(bindable);
+		}
+	}
+}
+\ No newline at end of file