Initial import

1 files changed, 65 insertions, 0 deletions

diff --git a/Xamarin.Forms.Core/Interactivity/Behavior.cs b/Xamarin.Forms.Core/Interactivity/Behavior.cs
new file mode 100644
index 00000000..f8689041
--- /dev/null
+++ b/Xamarin.Forms.Core/Interactivity/Behavior.cs
@@ -0,0 +1,65 @@
+using System;
+
+namespace Xamarin.Forms
+{
+	public abstract class Behavior : BindableObject, IAttachedObject
+	{
+		internal Behavior(Type associatedType)
+		{
+			if (associatedType == null)
+				throw new ArgumentNullException("associatedType");
+			AssociatedType = associatedType;
+		}
+
+		protected Type AssociatedType { get; }
+
+		void IAttachedObject.AttachTo(BindableObject bindable)
+		{
+			if (bindable == null)
+				throw new ArgumentNullException("bindable");
+			if (!AssociatedType.IsInstanceOfType(bindable))
+				throw new InvalidOperationException("bindable not an instance of AssociatedType");
+			OnAttachedTo(bindable);
+		}
+
+		void IAttachedObject.DetachFrom(BindableObject bindable)
+		{
+			OnDetachingFrom(bindable);
+		}
+
+		protected virtual void OnAttachedTo(BindableObject bindable)
+		{
+		}
+
+		protected virtual void OnDetachingFrom(BindableObject bindable)
+		{
+		}
+	}
+
+	public abstract class Behavior<T> : Behavior where T : BindableObject
+	{
+		protected Behavior() : base(typeof(T))
+		{
+		}
+
+		protected override void OnAttachedTo(BindableObject bindable)
+		{
+			base.OnAttachedTo(bindable);
+			OnAttachedTo((T)bindable);
+		}
+
+		protected virtual void OnAttachedTo(T bindable)
+		{
+		}
+
+		protected override void OnDetachingFrom(BindableObject bindable)
+		{
+			OnDetachingFrom((T)bindable);
+			base.OnDetachingFrom(bindable);
+		}
+
+		protected virtual void OnDetachingFrom(T bindable)
+		{
+		}
+	}
+}
\ No newline at end of file