Started adding general purpose IValueConverters.

samples/XamlTestApplication/XamlTestApplication.csproj

@@ -84,6 +84,10 @@
     <None Include="App.config" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\..\src\Markup\Perspex.Markup\Perspex.Markup.csproj">
+      <Project>{6417e941-21bc-467b-a771-0de389353ce6}</Project>
+      <Name>Perspex.Markup</Name>
+    </ProjectReference>
     <ProjectReference Include="..\..\src\Perspex.Animation\Perspex.Animation.csproj">
       <Project>{D211E587-D8BC-45B9-95A4-F297C8FA5200}</Project>
       <Name>Perspex.Animation</Name>

samples/XamlTestApplicationPcl/StringNullOrEmpty.cs

@@ -1,33 +0,0 @@
-// 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 System;
-using System.Globalization;
-using Perspex;
-using Perspex.Markup;
-
-namespace XamlTestApplication
-{
-    public class StringNullOrEmpty : IValueConverter
-    {
-        public static readonly StringNullOrEmpty Instance = new StringNullOrEmpty();
-
-        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
-        {
-            if (value == null)
-            {
-                return true;
-            }
-            else
-            {
-                var s = value as string;
-                return s != null ? string.IsNullOrEmpty(s) : PerspexProperty.UnsetValue;
-            }
-        }
-
-        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
-        {
-            throw new NotImplementedException();
-        }
-    }
-}

samples/XamlTestApplicationPcl/TextBox.paml

@@ -27,7 +27,7 @@
                 <TextBlock Name="watermark"
                            Opacity="0.5"
                            Text="{TemplateBinding Watermark}"
-                           IsVisible="{TemplateBinding Path=Text, Converter={Static local:StringNullOrEmpty.Instance}}"/>
+                           IsVisible="{TemplateBinding Path=Text, Converter={Static StringConverters.NullOrEmpty}}"/>
                 <TextPresenter Name="PART_TextPresenter"
                                CaretIndex="{TemplateBinding CaretIndex}"
                                SelectionStart="{TemplateBinding SelectionStart}"

samples/XamlTestApplicationPcl/XamlTestApplicationPcl.csproj

@@ -41,7 +41,6 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="StringNullOrEmpty.cs" />
     <Compile Include="ViewModels\MainWindowViewModel.cs" />
     <Compile Include="ViewModels\TestItem.cs" />
     <Compile Include="ViewModels\TestNode.cs" />

src/Markup/Perspex.Markup.Xaml/Context/PerspexWiringContext.cs

@@ -61,8 +61,9 @@ namespace Perspex.Markup.Xaml.Context
 
             var forcedAssemblies = new[]
             {
-                typeof (Control),
-                typeof(Style)
+                typeof(Control),
+                typeof(Style),
+                typeof(IValueConverter),
             }.Select(t => t.GetTypeInfo().Assembly);
 
             foreach (var nsa in 

src/Markup/Perspex.Markup/FuncValueConverter.cs

@@ -0,0 +1,48 @@
+// 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 System;
+using System.Globalization;
+using Perspex.Utilities;
+
+namespace Perspex.Markup
+{
+    /// <summary>
+    /// A general purpose <see cref="IValueConverter"/> that uses a <see cref="Func{T1, TResult}"/>
+    /// to provide the converter logic.
+    /// </summary>
+    /// <typeparam name="TIn"></typeparam>
+    /// <typeparam name="TOut"></typeparam>
+    public class FuncValueConverter<TIn, TOut> : IValueConverter
+    {
+        private Func<TIn, TOut> _convert;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="FuncValueConverter{TIn, TOut}"/> class.
+        /// </summary>
+        /// <param name="convert">The convert function.</param>
+        public FuncValueConverter(Func<TIn, TOut> convert)
+        {
+            _convert = convert;
+        }
+
+        /// <inheritdoc/>
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            if (value is TIn || (value == null && TypeUtilities.AcceptsNull(typeof(TIn))))
+            {
+                return _convert((TIn)value);
+            }
+            else
+            {
+                return PerspexProperty.UnsetValue;
+            }
+        }
+
+        /// <inheritdoc/>
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

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

@@ -36,6 +36,9 @@
     <DocumentationFile>bin\Release\Perspex.Markup.XML</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="..\..\Shared\SharedAssemblyInfo.cs">
+      <Link>Properties\SharedAssemblyInfo.cs</Link>
+    </Compile>
     <Compile Include="Data\ExpressionNodeBuilder.cs" />
     <Compile Include="Data\ExpressionParseException.cs" />
     <Compile Include="Data\ExpressionSubject.cs" />
@@ -49,6 +52,8 @@
     <Compile Include="Data\PropertyAccessorNode.cs" />
     <Compile Include="Data\ExpressionNode.cs" />
     <Compile Include="Data\ExpressionObserver.cs" />
+    <Compile Include="FuncValueConverter.cs" />
+    <Compile Include="StringConverters.cs" />
     <Compile Include="DefaultValueConverter.cs" />
     <Compile Include="IValueConverter.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />

src/Markup/Perspex.Markup/Properties/AssemblyInfo.cs

@@ -1,32 +1,10 @@
-using System.Resources;
+// 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 System.Reflection;
+using Perspex.Metadata;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
 
-// General Information about an assembly is controlled through the following 
-// set of attributes. Change these attribute values to modify the information
-// associated with an assembly.
 [assembly: AssemblyTitle("Perspex.Markup")]
-[assembly: AssemblyDescription("")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("")]
-[assembly: AssemblyProduct("Perspex.Markup")]
-[assembly: AssemblyCopyright("Copyright ©  2015")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-[assembly: NeutralResourcesLanguage("en")]
-
-// Version information for an assembly consists of the following four values:
-//
-//      Major Version
-//      Minor Version 
-//      Build Number
-//      Revision
-//
-// You can specify all the values or you can default the Build and Revision Numbers 
-// by using the '*' as shown below:
-// [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]
-
+[assembly: XmlnsDefinition("https://github.com/perspex", "Perspex.Markup")]
 [assembly: InternalsVisibleTo("Perspex.Markup.UnitTests")]

src/Markup/Perspex.Markup/StringConverters.cs

@@ -0,0 +1,21 @@
+// 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 System;
+using System.Globalization;
+using Perspex.Utilities;
+
+namespace Perspex.Markup
+{
+    /// <summary>
+    /// Provides a set of useful <see cref="IValueConverter"/>s for working with string values.
+    /// </summary>
+    public static class StringConverters
+    {
+        /// <summary>
+        /// A value converter that returns true if the input string is null or an empty string.
+        /// </summary>
+        public static readonly IValueConverter NullOrEmpty =
+            new FuncValueConverter<string, bool>(x => string.IsNullOrEmpty(x));
+    }
+}

src/Perspex.Base/Utilities/TypeUtilities.cs

@@ -27,6 +27,17 @@ namespace Perspex.Utilities
             { typeof(short), new List<Type> { typeof(byte) } }
         };
 
+        /// <summary>
+        /// Returns a value indicating whether null can be assigned to the specified type.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        /// <returns>True if the type accepts null values; otherwise false.</returns>
+        public static bool AcceptsNull(Type type)
+        {
+            var t = type.GetTypeInfo();
+            return !t.IsValueType || (t.IsGenericType && (t.GetGenericTypeDefinition() == typeof(Nullable<>)));
+        }
+
         /// <summary>
         /// Try to cast a value to a type, using implicit conversions if possible.
         /// </summary>
@@ -40,9 +51,8 @@ namespace Perspex.Utilities
 
             if (value == null)
             {
-                var t = to.GetTypeInfo();
                 result = null;
-                return !t.IsValueType || (t.IsGenericType && (t.GetGenericTypeDefinition() == typeof(Nullable<>)));
+                return AcceptsNull(to);
             }
 
             var from = value.GetType();