Added binding ConverterParameter.

Closes #317.

src/Markup/Perspex.Markup.Xaml/Data/Binding.cs

@@ -19,6 +19,11 @@ namespace Perspex.Markup.Xaml.Data
         /// </summary>
         public IValueConverter Converter { get; set; }
 
+        /// <summary>
+        /// Gets or sets a parameter to pass to <see cref="Converter"/>.
+        /// </summary>
+        public object ConverterParameter { get; set; }
+
         /// <summary>
         /// Gets or sets the name of the element to use as the binding source.
         /// </summary>
@@ -115,7 +120,8 @@ namespace Perspex.Markup.Xaml.Data
             return new ExpressionSubject(
                 observer,
                 targetType,
-                Converter ?? DefaultValueConverter.Instance);
+                Converter ?? DefaultValueConverter.Instance,
+                ConverterParameter);
         }
 
         /// <summary>

src/Markup/Perspex.Markup.Xaml/MarkupExtensions/BindingExtension.cs

@@ -22,6 +22,7 @@ namespace Perspex.Markup.Xaml.MarkupExtensions
             return new Binding
             {
                 Converter = Converter,
+                ConverterParameter = ConverterParameter,
                 ElementName = ElementName,
                 Mode = Mode,
                 Path = Path,
@@ -29,6 +30,7 @@ namespace Perspex.Markup.Xaml.MarkupExtensions
         }
 
         public IValueConverter Converter { get; set; }
+        public object ConverterParameter { get; set; }
         public string ElementName { get; set; }
         public BindingMode Mode { get; set; }
         public string Path { get; set; }

src/Markup/Perspex.Markup/Data/ExpressionSubject.cs

@@ -34,7 +34,12 @@ namespace Perspex.Markup.Data
         /// <param name="inner">The <see cref="ExpressionObserver"/>.</param>
         /// <param name="targetType">The type to convert the value to.</param>
         /// <param name="converter">The value converter to use.</param>
-        public ExpressionSubject(ExpressionObserver inner, Type targetType, IValueConverter converter)
+        /// <param name="converterParameter">A parameter to pass to <paramref name="converter"/>.</param>
+        public ExpressionSubject(
+            ExpressionObserver inner, 
+            Type targetType, 
+            IValueConverter converter,
+            object converterParameter = null)
         {
             Contract.Requires<ArgumentNullException>(inner != null);
             Contract.Requires<ArgumentNullException>(targetType != null);
@@ -43,6 +48,7 @@ namespace Perspex.Markup.Data
             _inner = inner;
             _targetType = targetType;
             Converter = converter;
+            ConverterParameter = converterParameter;
         }
 
         /// <summary>
@@ -50,6 +56,11 @@ namespace Perspex.Markup.Data
         /// </summary>
         public IValueConverter Converter { get; }
 
+        /// <summary>
+        /// Gets a parameter to pass to <see cref="Converter"/>.
+        /// </summary>
+        public object ConverterParameter { get; }
+
         /// <inheritdoc/>
         string IDescription.Description => _inner.Expression;
 
@@ -70,7 +81,11 @@ namespace Perspex.Markup.Data
 
             if (type != null)
             {
-                var converted = Converter.ConvertBack(value, type, null, CultureInfo.CurrentUICulture);
+                var converted = Converter.ConvertBack(
+                    value, 
+                    type, 
+                    ConverterParameter, 
+                    CultureInfo.CurrentUICulture);
 
                 if (converted == PerspexProperty.UnsetValue)
                 {
@@ -85,7 +100,11 @@ namespace Perspex.Markup.Data
         public IDisposable Subscribe(IObserver<object> observer)
         {
             return _inner
-                .Select(x => Converter.Convert(x, _targetType, null, CultureInfo.CurrentUICulture))
+                .Select(x => Converter.Convert(
+                    x, 
+                    _targetType, 
+                    ConverterParameter, 
+                    CultureInfo.CurrentUICulture))
                 .Subscribe(observer);
         }
     }

tests/Perspex.Markup.UnitTests/Data/ExpressionSubjectTests.cs

@@ -1,7 +1,11 @@
 // 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.ComponentModel;
+using System.Globalization;
 using System.Reactive.Linq;
+using Moq;
 using Perspex.Markup.Data;
 using Xunit;
 
@@ -125,11 +129,50 @@ namespace Perspex.Markup.UnitTests.Data
             Assert.Equal(0, data.DoubleValue);
         }
 
-        private class Class1
+        [Fact]
+        public void Should_Pass_ConverterParameter_To_Convert()
         {
+            var data = new Class1 { DoubleValue = 5.6 };
+            var converter = new Mock<IValueConverter>();
+            var target = new ExpressionSubject(
+                new ExpressionObserver(data, "DoubleValue"),
+                typeof(string),
+                converter.Object,
+                "foo");
+
+            target.Subscribe(_ => { });
+
+            converter.Verify(x => x.Convert(5.6, typeof(string), "foo", CultureInfo.CurrentUICulture));
+        }
+
+        [Fact]
+        public void Should_Pass_ConverterParameter_To_ConvertBack()
+        {
+            var data = new Class1 { DoubleValue = 5.6 };
+            var converter = new Mock<IValueConverter>();
+            var target = new ExpressionSubject(
+                new ExpressionObserver(data, "DoubleValue"), 
+                typeof(string),
+                converter.Object,
+                "foo");
+
+            target.OnNext("bar");
+
+            converter.Verify(x => x.ConvertBack("bar", typeof(double), "foo", CultureInfo.CurrentUICulture));
+        }
+
+        private class Class1 : INotifyPropertyChanged
+        {
+            public event PropertyChangedEventHandler PropertyChanged;
+
             public string StringValue { get; set; }
 
             public double DoubleValue { get; set; }
+
+            public void RaisePropertyChanged(string propertyName)
+            {
+                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+            }
         }
     }
 }

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

@@ -39,6 +39,10 @@
       <Private>True</Private>
     </Reference>
     <Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />
+    <Reference Include="Moq, Version=4.2.1507.118, Culture=neutral, PublicKeyToken=69f491c39445e920, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\Moq.4.2.1507.0118\lib\net40\Moq.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
     <Reference Include="System.Reactive.Core, Version=2.2.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">

tests/Perspex.Markup.UnitTests/packages.config

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="Moq" version="4.2.1507.0118" targetFramework="net46" />
   <package id="Rx-Core" version="2.2.5" targetFramework="net46" />
   <package id="Rx-Interfaces" version="2.2.5" targetFramework="net46" />
   <package id="Rx-Linq" version="2.2.5" targetFramework="net46" />

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

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Globalization;
 using System.Reactive.Linq;
 using System.Reactive.Subjects;
 using Moq;
@@ -169,6 +170,23 @@ namespace Perspex.Markup.Xaml.UnitTests.Data
             Assert.Same(converter.Object, ((ExpressionSubject)result).Converter);
         }
 
+        [Fact]
+        public void Should_Pass_ConverterParameter_To_Supplied_Converter()
+        {
+            var target = CreateTarget();
+            var converter = new Mock<IValueConverter>();
+            var binding = new Binding
+            {
+                Converter = converter.Object,
+                ConverterParameter = "foo",
+                Path = "Bar",
+            };
+
+            var result = binding.CreateSubject(target.Object, TextBox.TextProperty.PropertyType);
+
+            Assert.Same("foo", ((ExpressionSubject)result).ConverterParameter);
+        }
+
         /// <summary>
         /// Tests a problem discovered with ListBox with selection.
         /// </summary>