Slightly change the selector syntax.

Perspex.UnitTests/StyleTests.cs

@@ -18,7 +18,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Style_With_Only_Type_Selector_Should_Update_Value()
         {
-            Style style = new Style(new Selector().OfType<Class1>())
+            Style style = new Style(x => x.OfType<Class1>())
             {
                 Setters = new[]
                 {
@@ -36,7 +36,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Style_With_Class_Selector_Should_Update_And_Restore_Value()
         {
-            Style style = new Style(new Selector().OfType<Class1>().Class("foo"))
+            Style style = new Style(x => x.OfType<Class1>().Class("foo"))
             {
                 Setters = new[]
                 {
@@ -57,7 +57,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void LocalValue_Should_Override_Style()
         {
-            Style style = new Style(new Selector().OfType<Class1>())
+            Style style = new Style(x => x.OfType<Class1>())
             {
                 Setters = new[]
                 {
@@ -79,7 +79,7 @@ namespace Perspex.UnitTests
         {
             Styles styles = new Styles
             {
-                new Style(new Selector().OfType<Class1>().Class("foo"))
+                new Style(x => x.OfType<Class1>().Class("foo"))
                 {
                     Setters = new[]
                     {
@@ -87,7 +87,7 @@ namespace Perspex.UnitTests
                     },
                 },
 
-                new Style(new Selector().OfType<Class1>().Class("foo"))
+                new Style(x => x.OfType<Class1>().Class("foo"))
                 {
                     Setters = new[]
                     {

Perspex/PerspexObject.cs

@@ -9,9 +9,6 @@ namespace Perspex
     using System;
     using System.Collections.Generic;
     using System.Linq;
-    using System.Linq.Expressions;
-    using System.Reactive;
-    using System.Reactive.Disposables;
     using System.Reactive.Linq;
     using System.Reflection;
     using Splat;

Perspex/Styling/Style.cs

@@ -20,10 +20,10 @@ namespace Perspex.Styling
             this.Setters = new List<Setter>();
         }
 
-        public Style(Selector selector)
+        public Style(Func<Selector, Selector> selector)
             : this()
         {
-            this.Selector = selector;
+            this.Selector = selector(new Selector());
         }
 
         public Selector Selector

Perspex/Themes/Default/ButtonStyle.cs

@@ -15,14 +15,14 @@ namespace Perspex.Themes.Default
         {
             this.AddRange(new[]
             {
-                new Style(new Selector().OfType<Button>())
+                new Style(x => x.OfType<Button>())
                 {
                     Setters = new[]
                     {
                         new Setter(Button.TemplateProperty, ControlTemplate.Create<Button>(this.Template)),
                     },
                 },
-                new Style(new Selector().OfType<Button>().Template().Id("border"))
+                new Style(x => x.OfType<Button>().Template().Id("border"))
                 {
                     Setters = new[]
                     {
@@ -32,7 +32,7 @@ namespace Perspex.Themes.Default
                         new Setter(Button.ForegroundProperty, new SolidColorBrush(0xff000000)),
                     },
                 },
-                new Style(new Selector().OfType<Button>().Class(":mouseover").Template().Id("border"))
+                new Style(x => x.OfType<Button>().Class(":mouseover").Template().Id("border"))
                 {
                     Setters = new[]
                     {
@@ -40,7 +40,7 @@ namespace Perspex.Themes.Default
                         new Setter (Button.BorderBrushProperty, new SolidColorBrush(0xff3c7fb1)),
                     },
                 },
-                new Style(new Selector().OfType<Button>().Class(":pressed").Template().Id("border"))
+                new Style(x => x.OfType<Button>().Class(":pressed").Template().Id("border"))
                 {
                     Setters = new[]
                     {
@@ -56,11 +56,17 @@ namespace Perspex.Themes.Default
             Border border = new Border();
             border.Id = "border";
             border.Padding = new Thickness(3);
+            border.Bind(
+                Border.BackgroundProperty,
+                control.GetObservable(Button.BackgroundProperty),
+                BindingPriority.Template);
+
             ContentPresenter contentPresenter = new ContentPresenter();
             contentPresenter.Bind(
                 ContentPresenter.ContentProperty, 
                 control.GetObservable(Button.ContentProperty),
                 BindingPriority.Template);
+
             border.Content = contentPresenter;
             return border;
         }

TestApplication/Program.cs

@@ -52,6 +52,7 @@ namespace TestApplication
             {
                 Content = new Button
                 {
+                    Background = new SolidColorBrush(0xff0000ff),
                     Content = "Hello World",
                     HorizontalAlignment = HorizontalAlignment.Center,
                     VerticalAlignment = VerticalAlignment.Center,