Log binding path.

src/Markup/Perspex.Markup/Binding/ExpressionObserver.cs

@@ -10,7 +10,7 @@ namespace Perspex.Markup.Binding
     /// <summary>
     /// Observes and sets the value of an expression on an object.
     /// </summary>
-    public class ExpressionObserver : ObservableBase<ExpressionValue>
+    public class ExpressionObserver : ObservableBase<ExpressionValue>, IDescription
     {
         private object _root;
         private int _count;
@@ -25,6 +25,7 @@ namespace Perspex.Markup.Binding
         {
             _root = root;
             _node = ExpressionNodeBuilder.Build(expression);
+            Expression = expression;
         }
 
         /// <summary>
@@ -49,6 +50,11 @@ namespace Perspex.Markup.Binding
             }
         }
 
+        /// <summary>
+        /// Gets the expression being observed.
+        /// </summary>
+        public string Expression { get; }
+
         /// <summary>
         /// Gets or sets the root object that the expression is being observed on.
         /// </summary>
@@ -73,6 +79,9 @@ namespace Perspex.Markup.Binding
             }
         }
 
+        /// <inheritdoc/>
+        string IDescription.Description => Expression;
+
         /// <inheritdoc/>
         protected override IDisposable SubscribeCore(IObserver<ExpressionValue> observer)
         {

src/Markup/Perspex.Markup/Binding/ExpressionSubject.cs

@@ -10,7 +10,7 @@ namespace Perspex.Markup.Binding
     /// <summary>
     /// Turns an <see cref="ExpressionObserver"/> into a subject that can be bound two-ways.
     /// </summary>
-    public class ExpressionSubject : ISubject<object>
+    public class ExpressionSubject : ISubject<object>, IDescription
     {
         private ExpressionObserver _inner;
 
@@ -23,6 +23,9 @@ namespace Perspex.Markup.Binding
             _inner = inner;
         }
 
+        /// <inheritdoc/>
+        string IDescription.Description => _inner.Expression;
+
         /// <inheritdoc/>
         public void OnCompleted()
         {

src/Markup/Perspex.Markup/Perspex.Markup.csproj

@@ -71,6 +71,12 @@
   <ItemGroup>
     <None Include="packages.config" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Perspex.Base\Perspex.Base.csproj">
+      <Project>{b09b78d8-9b26-48b0-9149-d64a2f120f3f}</Project>
+      <Name>Perspex.Base</Name>
+    </ProjectReference>
+  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

src/Perspex.Base/PerspexObject.cs

@@ -335,7 +335,7 @@ namespace Perspex
                         PropertyChanged -= handler;
                     });
                 },
-                GetObservableDescription(property));
+                GetDescription(property));
         }
 
         /// <summary>
@@ -378,7 +378,7 @@ namespace Perspex
                         PropertyChanged -= handler;
                     });
                 },
-                GetObservableDescription(property));
+                GetDescription(property));
         }
 
         /// <summary>
@@ -591,14 +591,13 @@ namespace Perspex
                 _propertyLog.Verbose(
                     "Bound {Property} to {Binding} with priority LocalValue",
                     property,
-                    source);
+                    GetDescription(source));
 
                 return source.Subscribe(x => SetValue(property, x));
             }
             else
             {
                 PriorityValue v;
-                IDescription description = source as IDescription;
 
                 if (!IsRegistered(property))
                 {
@@ -614,7 +613,7 @@ namespace Perspex
                 _propertyLog.Verbose(
                     "Bound {Property} to {Binding} with priority {Priority}",
                     property,
-                    source,
+                    GetDescription(source),
                     priority);
 
                 return v.Add(source, (int)priority);
@@ -706,7 +705,7 @@ namespace Perspex
             _propertyLog.Verbose(
                 "Bound two way {Property} to {Binding} with priority {Priority}",
                 property,
-                source,
+                GetDescription(source),
                 priority);
 
             return new CompositeDisposable(
@@ -959,11 +958,22 @@ namespace Perspex
         /// </summary>
         /// <param name="property">The property</param>
         /// <returns>The description.</returns>
-        private string GetObservableDescription(PerspexProperty property)
+        private string GetDescription(PerspexProperty property)
         {
             return string.Format("{0}.{1}", GetType().Name, property.Name);
         }
 
+        /// <summary>
+        /// Gets a description of an observable that van be used in logs.
+        /// </summary>
+        /// <param name="o">The observable.</param>
+        /// <returns>The description.</returns>
+        private string GetDescription(IObservable<object> o)
+        {
+            var description = o as IDescription;
+            return description?.Description ?? o.ToString();
+        }
+
         /// <summary>
         /// Logs a property set message.
         /// </summary>

tests/Perspex.Markup.UnitTests/Perspex.Markup.UnitTests.csproj

@@ -91,6 +91,10 @@
       <Project>{6417e941-21bc-467b-a771-0de389353ce6}</Project>
       <Name>Perspex.Markup</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\src\Perspex.Base\Perspex.Base.csproj">
+      <Project>{b09b78d8-9b26-48b0-9149-d64a2f120f3f}</Project>
+      <Name>Perspex.Base</Name>
+    </ProjectReference>
   </ItemGroup>
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />