Add support for indexers in binding expressions.

src/Markup/Perspex.Markup/Binding/ElementAccessorNode.cs

@@ -0,0 +1,107 @@
+// 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;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Linq;
+using System.Reflection;
+
+namespace Perspex.Markup.Binding
+{
+    internal class ElementAccessorNode : ExpressionNode
+    {
+        private int[] _intArgs;
+
+        public ElementAccessorNode(ExpressionNode next, IList<object> arguments)
+            : base(next)
+        {
+            Arguments = arguments;
+
+            var intArgs = Arguments.OfType<int>().ToArray();
+
+            if (intArgs.Length == arguments.Count)
+            {
+                _intArgs = intArgs;
+            }
+        }
+
+        public IList<object> Arguments { get; }
+
+        protected override void SubscribeAndUpdate(object target)
+        {
+            CurrentValue = GetValue(target);
+
+            var incc = target as INotifyCollectionChanged;
+
+            if (incc != null)
+            {
+                incc.CollectionChanged += CollectionChanged;
+            }
+        }
+
+        protected override void Unsubscribe(object target)
+        {
+            var incc = target as INotifyCollectionChanged;
+
+            if (incc != null)
+            {
+                incc.CollectionChanged -= CollectionChanged;
+            }
+        }
+
+        private void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            bool update = false;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    update = _intArgs[0] >= e.NewStartingIndex;
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    update = _intArgs[0] >= e.OldStartingIndex;
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                    update = _intArgs[0] >= e.NewStartingIndex &&
+                             _intArgs[0] < e.NewStartingIndex + e.NewItems.Count;
+                    break;
+                case NotifyCollectionChangedAction.Move:
+                    update = (_intArgs[0] >= e.NewStartingIndex &&
+                              _intArgs[0] < e.NewStartingIndex + e.NewItems.Count) ||
+                             (_intArgs[0] >= e.OldStartingIndex &&
+                             _intArgs[0] < e.OldStartingIndex + e.OldItems.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    update = true;
+                    break;
+            }
+
+            if (update)
+            {
+                CurrentValue = GetValue(sender);
+            }
+        }
+
+        private ExpressionValue GetValue(object target)
+        {
+            var typeInfo = target.GetType().GetTypeInfo();
+            var list = target as IList;
+
+            if (typeInfo.IsArray && _intArgs != null)
+            {
+                return new ExpressionValue(((Array)target).GetValue(_intArgs));
+            }
+            else if (target is IList && _intArgs?.Length == 1)
+            {
+                if (_intArgs[0] < list.Count)
+                {
+                    return new ExpressionValue(list[_intArgs[0]]);
+                }
+            }
+
+            return ExpressionValue.None;
+        }
+    }
+}

src/Markup/Perspex.Markup/Binding/ExpressionNode.cs

@@ -95,9 +95,13 @@ namespace Perspex.Markup.Binding
             }
         }
 
-        protected abstract void SubscribeAndUpdate(object target);
-
-        protected abstract void Unsubscribe(object target);
+        protected virtual void SubscribeAndUpdate(object target)
+        {
+            CurrentValue = new ExpressionValue(target);
+        }
 
+        protected virtual void Unsubscribe(object target)
+        {
+        }
     }
 }

src/Markup/Perspex.Markup/Binding/ExpressionNodeBuilder.cs

@@ -39,6 +39,7 @@ namespace Perspex.Markup.Binding
             var identifier = syntax as IdentifierNameSyntax;
             var memberAccess = syntax as MemberAccessExpressionSyntax;
             var unaryExpression = syntax as PrefixUnaryExpressionSyntax;
+            var elementAccess = syntax as ElementAccessExpressionSyntax;
 
             if (expressionStatement != null)
             {
@@ -58,6 +59,11 @@ namespace Perspex.Markup.Binding
                 next = Build(expression, unaryExpression.Operand, next);
                 next = new LogicalNotNode(next);
             }
+            else if (elementAccess != null)
+            {
+                next = Build(expression, elementAccess, next);
+                next = Build(expression, elementAccess.Expression, next);
+            }
             else
             {
                 throw new Exception($"Invalid expression: {expression}");
@@ -65,5 +71,35 @@ namespace Perspex.Markup.Binding
 
             return next;
         }
+
+        private static ExpressionNode Build(string expression, ElementAccessExpressionSyntax syntax, ExpressionNode next)
+        {
+            var argList = syntax.ArgumentList as BracketedArgumentListSyntax;
+
+            if (argList != null)
+            {
+                var args = new List<object>();
+
+                foreach (var arg in argList.Arguments)
+                {
+                    var literal = arg.Expression as LiteralExpressionSyntax;
+
+                    if (literal != null)
+                    {
+                        args.Add(literal.Token.Value);
+                    }
+                    else
+                    {
+                        throw new Exception($"Invalid expression: {expression}");
+                    }
+                }
+
+                return new ElementAccessorNode(next, args);
+            }
+            else
+            {
+                throw new Exception($"Invalid expression: {expression}");
+            }
+        }
     }
 }

src/Markup/Perspex.Markup/Binding/LogicalNotNode.cs

@@ -24,15 +24,6 @@ namespace Perspex.Markup.Binding
             return Next.Select(x => Negate(x)).Subscribe(observer);
         }
 
-        protected override void SubscribeAndUpdate(object target)
-        {
-            CurrentValue = new ExpressionValue(target);
-        }
-
-        protected override void Unsubscribe(object target)
-        {
-        }
-
         private ExpressionValue Negate(ExpressionValue v)
         {
             if (v.HasValue)

src/Markup/Perspex.Markup/Binding/PropertyAccessorNode.cs

@@ -65,14 +65,6 @@ namespace Perspex.Markup.Binding
             CurrentValue = result;
         }
 
-        private void PropertyChanged(object sender, PropertyChangedEventArgs e)
-        {
-            if (e.PropertyName == PropertyName)
-            {
-                CurrentValue = new ExpressionValue(_propertyInfo.GetValue(Target));
-            }
-        }
-
         protected override void Unsubscribe(object target)
         {
             var inpc = target as INotifyPropertyChanged;
@@ -82,5 +74,13 @@ namespace Perspex.Markup.Binding
                 inpc.PropertyChanged -= PropertyChanged;
             }
         }
+
+        private void PropertyChanged(object sender, PropertyChangedEventArgs e)
+        {
+            if (e.PropertyName == PropertyName)
+            {
+                CurrentValue = new ExpressionValue(_propertyInfo.GetValue(Target));
+            }
+        }
     }
 }

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

@@ -37,6 +37,7 @@
     <Compile Include="Binding\ExpressionNodeBuilder.cs" />
     <Compile Include="Binding\ExpressionValue.cs" />
     <Compile Include="Binding\LogicalNotNode.cs" />
+    <Compile Include="Binding\ElementAccessorNode.cs" />
     <Compile Include="Binding\PropertyAccessorNode.cs" />
     <Compile Include="Binding\ExpressionNode.cs" />
     <Compile Include="Binding\ExpressionObserver.cs" />

tests/Perspex.Markup.UnitTests/Binding/ExpressionNodeBuilderTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System.Collections.Generic;
+using System.Linq;
 using Perspex.Markup.Binding;
 using Xunit;
 
@@ -24,9 +25,9 @@ namespace Perspex.Markup.UnitTests.Binding
             var result = ToList(ExpressionNodeBuilder.Build("Foo.Bar.Baz"));
 
             Assert.Equal(3, result.Count);
-            Assert.IsType<PropertyAccessorNode>(result[0]);
-            Assert.IsType<PropertyAccessorNode>(result[1]);
-            Assert.IsType<PropertyAccessorNode>(result[2]);
+            AssertIsProperty(result[0], "Foo");
+            AssertIsProperty(result[1], "Bar");
+            AssertIsProperty(result[2], "Baz");
         }
 
         [Fact]
@@ -36,9 +37,9 @@ namespace Perspex.Markup.UnitTests.Binding
 
             Assert.Equal(4, result.Count);
             Assert.IsType<LogicalNotNode>(result[0]);
-            Assert.IsType<PropertyAccessorNode>(result[1]);
-            Assert.IsType<PropertyAccessorNode>(result[2]);
-            Assert.IsType<PropertyAccessorNode>(result[3]);
+            AssertIsProperty(result[1], "Foo");
+            AssertIsProperty(result[2], "Bar");
+            AssertIsProperty(result[3], "Baz");
         }
 
         [Fact]
@@ -49,9 +50,60 @@ namespace Perspex.Markup.UnitTests.Binding
             Assert.Equal(5, result.Count);
             Assert.IsType<LogicalNotNode>(result[0]);
             Assert.IsType<LogicalNotNode>(result[1]);
-            Assert.IsType<PropertyAccessorNode>(result[2]);
-            Assert.IsType<PropertyAccessorNode>(result[3]);
-            Assert.IsType<PropertyAccessorNode>(result[4]);
+            AssertIsProperty(result[2], "Foo");
+            AssertIsProperty(result[3], "Bar");
+            AssertIsProperty(result[4], "Baz");
+        }
+
+        [Fact]
+        public void Should_Build_Indexed_Property()
+        {
+            var result = ToList(ExpressionNodeBuilder.Build("Foo[5]"));
+
+            Assert.Equal(2, result.Count);
+            AssertIsProperty(result[0], "Foo");
+            AssertIsIndexer(result[1], 5);
+            Assert.IsType<ElementAccessorNode>(result[1]);
+            Assert.Equal(new object[] { 5 }, ((ElementAccessorNode)result[1]).Arguments.ToArray());
+        }
+
+        [Fact]
+        public void Should_Build_Multiple_Indexed_Property()
+        {
+            var result = ToList(ExpressionNodeBuilder.Build("Foo[5, 6]"));
+
+            Assert.Equal(2, result.Count);
+            AssertIsProperty(result[0], "Foo");
+            Assert.IsType<ElementAccessorNode>(result[1]);
+            Assert.Equal(new object[] { 5, 6 }, ((ElementAccessorNode)result[1]).Arguments.ToArray());
+        }
+
+        [Fact]
+        public void Should_Build_Indexed_Property_In_Chain()
+        {
+            var result = ToList(ExpressionNodeBuilder.Build("Foo.Bar[5, 6].Baz"));
+
+            Assert.Equal(4, result.Count);
+            AssertIsProperty(result[0], "Foo");
+            AssertIsProperty(result[1], "Bar");
+            Assert.IsType<ElementAccessorNode>(result[2]);
+            AssertIsProperty(result[3], "Baz");
+        }
+
+        private void AssertIsProperty(ExpressionNode node, string name)
+        {
+            Assert.IsType<PropertyAccessorNode>(node);
+
+            var p = (PropertyAccessorNode)node;
+            Assert.Equal(name, p.PropertyName);
+        }
+
+        private void AssertIsIndexer(ExpressionNode node, params object[] args)
+        {
+            Assert.IsType<ElementAccessorNode>(node);
+
+            var e = (ElementAccessorNode)node;
+            Assert.Equal(e.Arguments.ToArray(), args.ToArray());
         }
 
         private List<ExpressionNode> ToList(ExpressionNode node)

tests/Perspex.Markup.UnitTests/Binding/ExpressionObserverTests_Indexer.cs

@@ -0,0 +1,113 @@
+// 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.Collections.ObjectModel;
+using System.Reactive.Linq;
+using Perspex.Markup.Binding;
+using Xunit;
+
+namespace Perspex.Markup.UnitTests.Binding
+{
+    public class ExpressionObserverTests_Indexer
+    {
+        [Fact]
+        public async void Should_Get_Array_Value()
+        {
+            var data = new { Foo = new [] { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[1]");
+            var result = await target.Take(1);
+
+            Assert.True(result.HasValue);
+            Assert.Equal("bar", result.Value);
+        }
+
+        [Fact]
+        public async void Should_Get_MultiDimensional_Array_Value()
+        {
+            var data = new { Foo = new[,] { { "foo", "bar" }, { "baz", "qux" } } };
+            var target = new ExpressionObserver(data, "Foo[1, 1]");
+            var result = await target.Take(1);
+
+            Assert.True(result.HasValue);
+            Assert.Equal("qux", result.Value);
+        }
+
+        [Fact]
+        public async void Should_Get_List_Value()
+        {
+            var data = new { Foo = new List<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[1]");
+            var result = await target.Take(1);
+
+            Assert.True(result.HasValue);
+            Assert.Equal("bar", result.Value);
+        }
+
+        [Fact]
+        public void Should_Track_INCC_Add()
+        {
+            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[2]");
+            var result = new List<object>();
+
+            var sub = target.Subscribe(x => result.Add(x.Value));
+            data.Foo.Add("baz");
+
+            Assert.Equal(new[] { null, "baz" }, result);
+        }
+
+        [Fact]
+        public void Should_Track_INCC_Remove()
+        {
+            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[0]");
+            var result = new List<object>();
+
+            var sub = target.Subscribe(x => result.Add(x.Value));
+            data.Foo.RemoveAt(0);
+
+            Assert.Equal(new[] { "foo", "bar" }, result);
+        }
+
+        [Fact]
+        public void Should_Track_INCC_Replace()
+        {
+            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[1]");
+            var result = new List<object>();
+
+            var sub = target.Subscribe(x => result.Add(x.Value));
+            data.Foo[1] = "baz";
+
+            Assert.Equal(new[] { "bar", "baz" }, result);
+        }
+
+        [Fact]
+        public void Should_Track_INCC_Move()
+        {
+            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[1]");
+            var result = new List<object>();
+
+            var sub = target.Subscribe(x => result.Add(x.Value));
+            data.Foo.Move(0, 1);
+
+            Assert.Equal(new[] { "bar", "foo" }, result);
+        }
+
+        [Fact]
+        public void Should_Track_INCC_Reset()
+        {
+            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+            var target = new ExpressionObserver(data, "Foo[1]");
+            var result = new List<object>();
+
+            var sub = target.Subscribe(x => result.Add(x.Value));
+            data.Foo.Clear();
+
+            Assert.Equal(new[] { "bar", null }, result);
+        }
+    }
+}

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

@@ -72,6 +72,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Binding\ExpressionObserverTests_Indexer.cs" />
     <Compile Include="Binding\ExpressionObserverTests_Negation.cs" />
     <Compile Include="Binding\ExpressionObserverTests_Property.cs" />
     <Compile Include="Binding\ExpressionNodeBuilderTests.cs" />