add Screenshot

src/Shared/HandyControl_Shared/Interactivity/Behavior/Behavior!1.cs

@@ -0,0 +1,13 @@
+using System.Windows;
+
+namespace HandyControl.Interactivity
+{
+    public abstract class Behavior<T> : Behavior where T : DependencyObject
+    {
+        protected Behavior() : base(typeof(T))
+        {
+        }
+
+        protected new T AssociatedObject => (T)base.AssociatedObject;
+    }
+}