Make DataTemplate match derived types.

Closes #251.

src/Markup/Perspex.Markup.Xaml/Templates/DataTemplate.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.Reflection;
 using OmniXaml.Attributes;
 using Perspex.Controls;
 using Perspex.Controls.Templates;
@@ -20,7 +21,7 @@ namespace Perspex.Markup.Xaml.Templates
                 throw new InvalidOperationException("DataTemplate must have a DataType.");
             }
 
-            return DataType == data.GetType();
+            return DataType.GetTypeInfo().IsAssignableFrom(data.GetType().GetTypeInfo());
         }
 
         public IControl Build(object data)

tests/Perspex.Markup.Xaml.UnitTests/Templates/DataTemplateTests.cs

@@ -0,0 +1,37 @@
+// 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.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Perspex.Markup.Xaml.Templates;
+using Xunit;
+
+namespace Perspex.Markup.Xaml.UnitTests.Templates
+{
+    public class DataTemplateTests
+    {
+        [Fact]
+        public void DataTemplate_Should_Match_Data_Of_Type()
+        {
+            var target = new DataTemplate { DataType = typeof(Class1) };
+            var data = new Class1();
+
+            Assert.True(target.Match(data));
+        }
+
+        [Fact]
+        public void DataTemplate_Should_Match_Data_Of_Derived_Type()
+        {
+            var target = new DataTemplate { DataType = typeof(Class1) };
+            var data = new Class2();
+
+            Assert.True(target.Match(data));
+        }
+
+        private class Class1 { }
+        private class Class2 : Class1 { }
+    }
+}