added overload for EA to provide filter

src/Prism.Core/Events/PubSubEvent.cs

@@ -153,6 +153,17 @@ public SubscriptionToken Subscribe(Action<TPayload> action)
             return Subscribe(action, ThreadOption.PublisherThread);
         }
 
+        /// <summary>
+        /// Subscribes a delegate to an event that will be published on the <see cref="ThreadOption.PublisherThread"/>
+        /// </summary>
+        /// <param name="action">The delegate that gets executed when the event is raised.</param>
+        /// <param name="filter">Filter to evaluate if the subscriber should receive the event.</param>
+        /// <returns>A <see cref="SubscriptionToken"/> that uniquely identifies the added subscription.</returns>
+        public virtual SubscriptionToken Subscribe(Action<TPayload> action, Predicate<TPayload> filter)
+        {
+            return Subscribe(action, ThreadOption.PublisherThread, false, filter);
+        }
+
         /// <summary>
         /// Subscribes a delegate to an event.
         /// PubSubEvent will maintain a <see cref="WeakReference"/> to the Target of the supplied <paramref name="action"/> delegate.

tests/Prism.Core.Tests/Events/PubSubEventFixture.cs

@@ -143,6 +143,24 @@ public void FilterEnablesActionTarget()
 
         }
 
+        [Fact]
+        public void FilterEnablesActionTarget_Weak()
+        {
+            TestablePubSubEvent<string> pubSubEvent = new TestablePubSubEvent<string>();
+            var goodFilter = new MockFilter { FilterReturnValue = true };
+            var actionGoodFilter = new ActionHelper();
+            var badFilter = new MockFilter { FilterReturnValue = false };
+            var actionBadFilter = new ActionHelper();
+            pubSubEvent.Subscribe(actionGoodFilter.Action, goodFilter.FilterString);
+            pubSubEvent.Subscribe(actionBadFilter.Action, badFilter.FilterString);
+
+            pubSubEvent.Publish("test");
+
+            Assert.True(actionGoodFilter.ActionCalled);
+            Assert.False(actionBadFilter.ActionCalled);
+
+        }
+
         [Fact]
         public void SubscribeDefaultsThreadOptionAndNoFilter()
         {