We can now override the default binding mode.

So make TextBlock and TextBox have different default binding modes.

src/Perspex.Base/PropertyMetadata.cs

@@ -11,19 +11,28 @@ namespace Perspex
     /// </summary>
     public class PropertyMetadata
     {
+        private BindingMode _defaultBindingMode;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PropertyMetadata"/> class.
         /// </summary>
         /// <param name="defaultBindingMode">The default binding mode.</param>
         public PropertyMetadata(BindingMode defaultBindingMode = BindingMode.Default)
         {
-            DefaultBindingMode = defaultBindingMode;
+            _defaultBindingMode = defaultBindingMode;
         }
 
         /// <summary>
         /// Gets the default binding mode for the property.
         /// </summary>
-        public BindingMode DefaultBindingMode { get; private set; }
+        public BindingMode DefaultBindingMode
+        {
+            get
+            {
+                return _defaultBindingMode == BindingMode.Default ?
+                    BindingMode.OneWay : _defaultBindingMode;
+            }
+        }
 
         /// <summary>
         /// Merges the metadata with the base metadata.
@@ -34,9 +43,9 @@ namespace Perspex
             PropertyMetadata baseMetadata, 
             PerspexProperty property)
         {
-            if (DefaultBindingMode == BindingMode.Default)
+            if (_defaultBindingMode == BindingMode.Default)
             {
-                DefaultBindingMode = baseMetadata.DefaultBindingMode;
+                _defaultBindingMode = baseMetadata.DefaultBindingMode;
             }
         }
     }

src/Perspex.Controls/TextBlock.cs

@@ -72,7 +72,7 @@ namespace Perspex.Controls
         /// Defines the <see cref="Text"/> property.
         /// </summary>
         public static readonly StyledProperty<string> TextProperty =
-            PerspexProperty.Register<TextBlock, string>(nameof(Text), defaultBindingMode: BindingMode.TwoWay);
+            PerspexProperty.Register<TextBlock, string>(nameof(Text));
 
         /// <summary>
         /// Defines the <see cref="TextAlignment"/> property.

src/Perspex.Controls/TextBox.cs

@@ -71,6 +71,7 @@ namespace Perspex.Controls
         static TextBox()
         {
             FocusableProperty.OverrideDefaultValue(typeof(TextBox), true);
+            TextProperty.OverrideMetadata<TextBox>(new StyledPropertyMetadata<string>(defaultBindingMode: BindingMode.TwoWay));
         }
 
         public TextBox()

tests/Perspex.Controls.UnitTests/TextBlockTests.cs

@@ -0,0 +1,19 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Perspex.Data;
+using Xunit;
+
+namespace Perspex.Controls.UnitTests
+{
+    public class TextBlockTests
+    {
+        [Fact]
+        public void DefaultBindingMode_Should_Be_OneWay()
+        {
+            Assert.Equal(
+                BindingMode.OneWay,
+                TextBlock.TextProperty.GetMetadata(typeof(TextBlock)).DefaultBindingMode);
+        }
+    }
+}

tests/Perspex.Controls.UnitTests/TextBoxTests.cs

@@ -0,0 +1,19 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Perspex.Data;
+using Xunit;
+
+namespace Perspex.Controls.UnitTests
+{
+    public class TextBoxTests
+    {
+        [Fact]
+        public void DefaultBindingMode_Should_Be_TwoWay()
+        {
+            Assert.Equal(
+                BindingMode.TwoWay,
+                TextBox.TextProperty.GetMetadata(typeof(TextBox)).DefaultBindingMode);
+        }
+    }
+}

tests/Perspex.Markup.Xaml.UnitTests/Data/BindingTests.cs

@@ -96,20 +96,19 @@ namespace Perspex.Markup.Xaml.UnitTests.Data
         [Fact]
         public void Default_BindingMode_Should_Be_Used()
         {
-            // Default for TextBox.Text is two-way.
             var source = new Source { Foo = "foo" };
-            var target = new TextBlock { DataContext = source };
+            var target = new TwoWayBindingTest { DataContext = source };
             var binding = new Binding
             {
                 Path = "Foo",
             };
 
-            target.Bind(TextBox.TextProperty, binding);
+            target.Bind(TwoWayBindingTest.TwoWayProperty, binding);
 
-            Assert.Equal("foo", target.Text);
+            Assert.Equal("foo", target.TwoWay);
             source.Foo = "bar";
-            Assert.Equal("bar", target.Text);
-            target.Text = "baz";
+            Assert.Equal("bar", target.TwoWay);
+            target.TwoWay = "baz";
             Assert.Equal("baz", source.Foo);
         }
 
@@ -260,6 +259,20 @@ namespace Perspex.Markup.Xaml.UnitTests.Data
             Assert.Equal(2, vm.Bar);
         }
 
+        private class TwoWayBindingTest : Control
+        {
+            public static readonly StyledProperty<string> TwoWayProperty =
+                PerspexProperty.Register<TwoWayBindingTest, string>(
+                    "TwoWay", 
+                    defaultBindingMode: BindingMode.TwoWay);
+
+            public string TwoWay
+            {
+                get { return GetValue(TwoWayProperty); }
+                set { SetValue(TwoWayProperty, value); }
+            }
+        }
+
         public class Source : ReactiveObject
         {
             private string _foo;