Added failing test.

tests/Avalonia.Base.UnitTests/Data/Core/TypedBindingExpressionTests_Property.cs

@@ -267,6 +267,32 @@ namespace Avalonia.Base.UnitTests.Data.Core
             GC.KeepAlive(data);
         }
 
+        [Fact]
+        public void Should_Ignore_Unrelated_Property_Changes()
+        {
+            var data = new Class1 { Next = new Class2 { Bar = "bar" } };
+            var binding = TypedBindingExpression.OneWay(data, o => (o.Next as Class2).Bar);
+            var result = new List<object>();
+
+            binding.Subscribe(x => result.Add(x.Value));
+
+            Assert.Equal(1, data.PropertyChangedSubscriptionCount);
+            Assert.Equal(1, data.Next.PropertyChangedSubscriptionCount);
+            Assert.Equal(1, data.PropertyChangedGeneration);
+            Assert.Equal(1, ((Class2)data.Next).PropertyChangedGeneration);
+            Assert.Equal(new[] { "bar" }, result);
+
+            data.Foo = "unrelated";
+
+            Assert.Equal(1, data.PropertyChangedSubscriptionCount);
+            Assert.Equal(1, data.Next.PropertyChangedSubscriptionCount);
+            Assert.Equal(1, data.PropertyChangedGeneration);
+            Assert.Equal(1, ((Class2)data.Next).PropertyChangedGeneration);
+            Assert.Equal(new[] { "bar" }, result);
+
+            GC.KeepAlive(data);
+        }
+
         [Fact]
         public void Empty_Expression_Should_Track_Root()
         {

tests/Avalonia.UnitTests/NotifyingBase.cs

@@ -14,6 +14,7 @@ namespace Avalonia.UnitTests
             {
                 _propertyChanged += value;
                 ++PropertyChangedSubscriptionCount;
+                ++PropertyChangedGeneration;
             }
 
             remove
@@ -22,15 +23,13 @@ namespace Avalonia.UnitTests
                 {
                     _propertyChanged -= value;
                     --PropertyChangedSubscriptionCount;
+                    ++PropertyChangedGeneration;
                 }
             }
         }
 
-        public int PropertyChangedSubscriptionCount
-        {
-            get;
-            private set;
-        }
+        public int PropertyChangedGeneration { get; private set; }
+        public int PropertyChangedSubscriptionCount { get; private set; }
 
         public void RaisePropertyChanged([CallerMemberName] string propertyName = null)
         {