From 395dc293f16111123dcdc6217647456bc4fe5694 Mon Sep 17 00:00:00 2001
From: Stephane Delcroix <stephane@delcroix.org>
Date: Tue, 3 Sep 2019 22:45:22 +0200
Subject: [PATCH] [X] Reuse baseclass namescope if it exists (#7356)

* [X] chain debug ctors

* unit test for 7097

* [X] Reuse baseclass namescope if it exists

If a xaml control derives from another xaml control, thy both should share the same
NameScope. This add a check if the xaml root already has a NameScope (set by the base)
and reuses it.

This fixes 2 regressions introduced by #7040 and some other unreported edge cases.

- fixes #7097
- fixes #7286

* avoid repeting linq queries
---
 Xamarin.Forms.Build.Tasks/DebugXamlCTask.cs   |  12 +-
 .../SetNamescopesAndRegisterNamesVisitor.cs   |  58 +++---
 Xamarin.Forms.Core/Internals/NameScope.cs     |   5 +-
 .../Issues/Gh7097.xaml                        |  34 ++++
 .../Issues/Gh7097.xaml.cs                     |  70 +++++++
 .../Issues/Gh7097Base.xaml                    |  14 ++
 .../Issues/Gh7097Base.xaml.cs                 |  16 ++
 .../MarkupExpressionParserTests.cs            |   6 +-
 Xamarin.Forms.Xaml/CreateValuesVisitor.cs     | 185 ++++++------------
 Xamarin.Forms.Xaml/NamescopingVisitor.cs      |  35 ++--
 Xamarin.Forms.Xaml/RegisterXNamesVisitor.cs   |  15 +-
 Xamarin.Forms.Xaml/XamlNode.cs                |  16 +-
 Xamarin.Forms.Xaml/XamlServiceProvider.cs     |  63 ++----
 13 files changed, 279 insertions(+), 250 deletions(-)
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml.cs
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml.cs

diff --git a/Xamarin.Forms.Build.Tasks/DebugXamlCTask.cs b/Xamarin.Forms.Build.Tasks/DebugXamlCTask.cs
index af934c52e..25be35bbd 100644
--- a/Xamarin.Forms.Build.Tasks/DebugXamlCTask.cs
+++ b/Xamarin.Forms.Build.Tasks/DebugXamlCTask.cs
@@ -113,8 +113,16 @@ namespace Xamarin.Forms.Build.Tasks
 						var br2 = Instruction.Create(OpCodes.Ldarg_0);
 						var ret = Instruction.Create(OpCodes.Ret);
 						il.Emit(OpCodes.Ldarg_0);
-						var baseCtor = module.ImportReference(typeDef.BaseType.Resolve().GetConstructors().First(c => c.HasParameters == false));
-						baseCtor = module.ImportReference(baseCtor.ResolveGenericParameters(typeDef.BaseType, module));
+						MethodReference baseCtor;
+						if (typeDef.BaseType.Resolve().GetConstructors().FirstOrDefault(c => c.HasParameters && c.Parameters.Count == 1 && c.Parameters[0].Name == "useCompiledXaml") is MethodDefinition baseCtorDef) {
+							baseCtor = module.ImportReference(baseCtorDef);
+							baseCtor = module.ImportReference(baseCtor.ResolveGenericParameters(typeDef.BaseType, module));
+							il.Emit(OpCodes.Ldarg_1);
+						}
+						else {
+							baseCtor = module.ImportReference(typeDef.BaseType.Resolve().GetConstructors().First(c => c.HasParameters == false));
+							baseCtor = module.ImportReference(baseCtor.ResolveGenericParameters(typeDef.BaseType, module));
+						}
 						il.Emit(OpCodes.Callvirt, baseCtor);
 
 						il.Emit(OpCodes.Nop);
diff --git a/Xamarin.Forms.Build.Tasks/SetNamescopesAndRegisterNamesVisitor.cs b/Xamarin.Forms.Build.Tasks/SetNamescopesAndRegisterNamesVisitor.cs
index edd435167..03b68a158 100644
--- a/Xamarin.Forms.Build.Tasks/SetNamescopesAndRegisterNamesVisitor.cs
+++ b/Xamarin.Forms.Build.Tasks/SetNamescopesAndRegisterNamesVisitor.cs
@@ -10,10 +10,7 @@ namespace Xamarin.Forms.Build.Tasks
 {
 	class SetNamescopesAndRegisterNamesVisitor : IXamlNodeVisitor
 	{
-		public SetNamescopesAndRegisterNamesVisitor(ILContext context)
-		{
-			Context = context;
-		}
+		public SetNamescopesAndRegisterNamesVisitor(ILContext context) => Context = context;
 
 		ILContext Context { get; }
 
@@ -25,7 +22,7 @@ namespace Xamarin.Forms.Build.Tasks
 
 		public bool IsResourceDictionary(ElementNode node)
 		{
-			var parentVar = Context.Variables[(IElementNode)node];
+			var parentVar = Context.Variables[node];
 			return parentVar.VariableType.FullName == "Xamarin.Forms.ResourceDictionary"
 				|| parentVar.VariableType.Resolve().BaseType?.FullName == "Xamarin.Forms.ResourceDictionary";
 		}
@@ -64,7 +61,7 @@ namespace Xamarin.Forms.Build.Tasks
 	
 		public void Visit(RootNode node, INode parentNode)
 		{
-			var namescopeVarDef = CreateNamescope();
+			var namescopeVarDef = GetOrCreateNameScope(node);
 			IList<string> namesInNamescope = new List<string>();
 			if (Context.Variables[node].VariableType.InheritsFromOrImplements(Context.Body.Method.Module.ImportReference(("Xamarin.Forms.Core", "Xamarin.Forms", "BindableObject"))))
 				SetNameScope(node, namescopeVarDef);
@@ -77,33 +74,38 @@ namespace Xamarin.Forms.Build.Tasks
 		}
 
 		static bool IsDataTemplate(INode node, INode parentNode)
-		{
-			var parentElement = parentNode as IElementNode;
-			INode createContent;
-			if (parentElement != null && parentElement.Properties.TryGetValue(XmlName._CreateContent, out createContent) &&
-			    createContent == node)
-				return true;
-			return false;
-		}
+			=> parentNode is IElementNode parentElement && parentElement.Properties.TryGetValue(XmlName._CreateContent, out INode createContent) && createContent == node;
 
-		static bool IsStyle(INode node, INode parentNode)
-		{
-			var pnode = parentNode as ElementNode;
-			return pnode != null && pnode.XmlType.Name == "Style";
-		}
+		static bool IsStyle(INode node, INode parentNode) => parentNode is ElementNode pnode && pnode.XmlType.Name == "Style";
 
-		static bool IsVisualStateGroupList(ElementNode node)
-		{
-			return node != null  && node.XmlType.Name == "VisualStateGroup" && node.Parent is IListNode;
-		}
+		static bool IsVisualStateGroupList(ElementNode node) => node != null && node.XmlType.Name == "VisualStateGroup" && node.Parent is IListNode;
 
 		static bool IsXNameProperty(ValueNode node, INode parentNode)
+			=> parentNode is IElementNode parentElement && parentElement.Properties.TryGetValue(XmlName.xName, out INode xNameNode) && xNameNode == node;
+
+		VariableDefinition GetOrCreateNameScope(ElementNode node)
 		{
-			var parentElement = parentNode as IElementNode;
-			INode xNameNode;
-			if (parentElement != null && parentElement.Properties.TryGetValue(XmlName.xName, out xNameNode) && xNameNode == node)
-				return true;
-			return false;
+			var module = Context.Body.Method.Module;
+			var vardef = new VariableDefinition(module.ImportReference(("Xamarin.Forms.Core", "Xamarin.Forms.Internals", "NameScope")));
+			Context.Body.Variables.Add(vardef);
+			var stloc = Instruction.Create(OpCodes.Stloc, vardef);
+
+			if (Context.Variables[node].VariableType.InheritsFromOrImplements(Context.Body.Method.Module.ImportReference(("Xamarin.Forms.Core", "Xamarin.Forms", "BindableObject")))) {
+				var namescoperef = ("Xamarin.Forms.Core", "Xamarin.Forms", "BindableObject");
+				Context.IL.Append(Context.Variables[node].LoadAs(module.GetTypeDefinition(namescoperef), module));
+				Context.IL.Emit(OpCodes.Call, module.ImportMethodReference(("Xamarin.Forms.Core", "Xamarin.Forms.Internals", "NameScope"),
+																		   methodName: "GetNameScope",
+																		   parameterTypes: new[] { namescoperef },
+																		   isStatic: true));
+				Context.IL.Emit(OpCodes.Dup);
+				Context.IL.Emit(OpCodes.Brtrue, stloc);
+
+				Context.IL.Emit(OpCodes.Pop);
+			}
+			Context.IL.Emit(OpCodes.Newobj, module.ImportCtorReference(("Xamarin.Forms.Core", "Xamarin.Forms.Internals", "NameScope"), parameterTypes: null));
+
+			Context.IL.Append(stloc);
+			return vardef;
 		}
 
 		VariableDefinition CreateNamescope()
diff --git a/Xamarin.Forms.Core/Internals/NameScope.cs b/Xamarin.Forms.Core/Internals/NameScope.cs
index 9419bf02b..bf20c1111 100644
--- a/Xamarin.Forms.Core/Internals/NameScope.cs
+++ b/Xamarin.Forms.Core/Internals/NameScope.cs
@@ -23,10 +23,7 @@ namespace Xamarin.Forms.Internals
 			_names[name] = scopedElement;
 		}
 
-		public static INameScope GetNameScope(BindableObject bindable)
-		{
-			return (INameScope)bindable.GetValue(NameScopeProperty);
-		}
+		public static INameScope GetNameScope(BindableObject bindable) => (INameScope)bindable.GetValue(NameScopeProperty);
 
 		public static void SetNameScope(BindableObject bindable, INameScope value)
 		{
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml
new file mode 100644
index 000000000..3a3e14ca9
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<local:Gh7097Base
+        xmlns="http://xamarin.com/schemas/2014/forms"
+        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+        xmlns:local="using:Xamarin.Forms.Xaml.UnitTests"
+        x:Class="Xamarin.Forms.Xaml.UnitTests.Gh7097"
+        Title="Foo"
+        x:Name="self">
+    <CollectionView ItemsSource="{Binding Items}" x:Name="collectionview">
+            <CollectionView.ItemsLayout>
+                <ListItemsLayout ItemSpacing="4">
+                    <x:Arguments>
+                        <ItemsLayoutOrientation>Vertical</ItemsLayoutOrientation>
+                    </x:Arguments>
+                </ListItemsLayout>
+            </CollectionView.ItemsLayout>
+            <CollectionView.ItemTemplate>
+                <DataTemplate>
+                    <StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand" BackgroundColor="Green">
+                        <Button 
+                            Text="BTN 1" 
+                            HorizontalOptions="FillAndExpand" 
+                            CommandParameter="{Binding}" 
+                            Command="{Binding BindingContext.Button1Command, Source={x:Reference self}}"/>
+                        <Button 
+                            Text="BTN 2" 
+                            HorizontalOptions="FillAndExpand" 
+                            CommandParameter="{Binding}" 
+                            Command="{Binding BindingContext.Button2Command, Source={x:Reference self}}"/>
+                    </StackLayout>
+                </DataTemplate>
+            </CollectionView.ItemTemplate>
+        </CollectionView>
+</local:Gh7097Base>
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml.cs b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml.cs
new file mode 100644
index 000000000..a92e31956
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097.xaml.cs
@@ -0,0 +1,70 @@
+using System;
+using System.Collections.Generic;
+using System.Windows.Input;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public partial class Gh7097 : Gh7097Base
+	{
+		public Gh7097() => InitializeComponent();
+		public Gh7097(bool useCompiledXaml) : base(useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		class Tests
+		{
+			IReadOnlyList<string> _flags;
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+				_flags = Device.Flags;
+				Device.SetFlags(new List<string>(Device.Flags ?? new List<string>()) { "CollectionView_Experimental" }.AsReadOnly());
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+				Device.SetFlags(_flags);
+			}
+
+			[Test]
+			public void CanXReferenceRoot([Values(false, true)]bool useCompiledXaml)
+			{
+				var layout = new Gh7097(useCompiledXaml) { BindingContext = new {
+						Button1Command = new MockCommand(),
+						Button2Command = new MockCommand(),
+					} };
+				var cv = layout.Content as CollectionView;
+				var content = cv.ItemTemplate.CreateContent() as StackLayout;
+				var btn1 = content.Children[0] as Button;
+				Assert.That(btn1.Command, Is.TypeOf<MockCommand>());
+			}
+
+			[Test]
+			//this was later reported as https://github.com/xamarin/Xamarin.Forms/issues/7286
+			public void RegisteringXNameOnSubPages([Values(false, true)]bool useCompiledXaml)
+			{
+				var layout = new Gh7097(useCompiledXaml);
+				var s = layout.FindByName("self");
+				Assert.That(layout.self, Is.Not.Null);
+				Assert.That(layout.collectionview, Is.Not.Null);
+			}
+
+			class MockCommand : ICommand
+			{
+#pragma warning disable 0067
+				public event EventHandler CanExecuteChanged;
+#pragma warning restore 0067
+				public bool CanExecute(object parameter) => true;
+				public void Execute(object parameter) => throw new NotImplementedException();
+			}
+		}
+	}
+}
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml
new file mode 100644
index 000000000..88152d3c1
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage
+        xmlns="http://xamarin.com/schemas/2014/forms"
+        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+        x:Class="Xamarin.Forms.Xaml.UnitTests.Gh7097Base">
+    <ContentPage.ControlTemplate>
+        <ControlTemplate>
+            <StackLayout>
+                <Label Text="BASE" FontSize="30" FontAttributes="Bold" HorizontalOptions="CenterAndExpand" TextColor="Red"/>
+                <ContentPresenter HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" />
+            </StackLayout>
+        </ControlTemplate>
+    </ContentPage.ControlTemplate>
+</ContentPage>
\ No newline at end of file
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml.cs b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml.cs
new file mode 100644
index 000000000..c94415ef6
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh7097Base.xaml.cs
@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+
+using Xamarin.Forms;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public partial class Gh7097Base : ContentPage
+	{
+		public Gh7097Base() => InitializeComponent();
+		public Gh7097Base(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+	}
+}
diff --git a/Xamarin.Forms.Xaml.UnitTests/MarkupExpressionParserTests.cs b/Xamarin.Forms.Xaml.UnitTests/MarkupExpressionParserTests.cs
index 37ba17008..806b63bd9 100644
--- a/Xamarin.Forms.Xaml.UnitTests/MarkupExpressionParserTests.cs
+++ b/Xamarin.Forms.Xaml.UnitTests/MarkupExpressionParserTests.cs
@@ -36,11 +36,7 @@ namespace Xamarin.Forms.Xaml.UnitTests
 
 			public List<XmlName> SkipProperties { get; set; }
 
-			public Forms.Internals.INameScope Namescope {
-				get {
-					throw new NotImplementedException ();
-				}
-			}
+			public NameScopeRef NameScopeRef => throw new NotImplementedException();
 
 			public XmlType XmlType {
 				get;
diff --git a/Xamarin.Forms.Xaml/CreateValuesVisitor.cs b/Xamarin.Forms.Xaml/CreateValuesVisitor.cs
index 88e71abb5..d7197f506 100644
--- a/Xamarin.Forms.Xaml/CreateValuesVisitor.cs
+++ b/Xamarin.Forms.Xaml/CreateValuesVisitor.cs
@@ -141,8 +141,8 @@ namespace Xamarin.Forms.Xaml
 				Values[node] = value;
 			}
 
-			if (value is BindableObject bindableValue && node.Namescope != (parentNode as IElementNode)?.Namescope)
-				NameScope.SetNameScope(bindableValue, node.Namescope);
+			if (value is BindableObject bindableValue && node.NameScopeRef != (parentNode as IElementNode)?.NameScopeRef)
+				NameScope.SetNameScope(bindableValue, node.NameScopeRef.NameScope);
 
 			if (XamlLoader.ValueCreatedCallback != null) {
 				var name = node.XmlType.Name;
@@ -157,16 +157,18 @@ namespace Xamarin.Forms.Xaml
 			var rnode = (XamlLoader.RuntimeRootNode)node;
 			Values[node] = rnode.Root;
 			Context.Types[node] = rnode.Root.GetType();
-			var bindableRoot = rnode.Root as BindableObject;
-			if (bindableRoot != null)
-				NameScope.SetNameScope(bindableRoot, node.Namescope);
+			if (rnode.Root is BindableObject bindable) {
+				if (NameScope.GetNameScope(bindable) is INameScope existingNs)
+					node.NameScopeRef.NameScope = existingNs;
+				else
+					NameScope.SetNameScope(bindable, node.NameScopeRef?.NameScope);
+			}
 		}
 
 		public void Visit(ListNode node, INode parentNode)
 		{
 			//this is a gross hack to keep ListNode alive. ListNode must go in favor of Properties
-			XmlName name;
-			if (ApplyPropertiesVisitor.TryGetPropertyName(node, parentNode, out name))
+			if (ApplyPropertiesVisitor.TryGetPropertyName(node, parentNode, out XmlName name))
 				node.XmlName = name;
 		}
 
@@ -181,14 +183,12 @@ namespace Xamarin.Forms.Xaml
 							ci.GetParameters().All(pi => pi.CustomAttributes.Any(attr => attr.AttributeType == typeof (ParameterAttribute))));
 			if (ctorInfo == null)
 				return true;
-			foreach (var parameter in ctorInfo.GetParameters())
-			{
+			foreach (var parameter in ctorInfo.GetParameters()) {
 				var propname =
 					parameter.CustomAttributes.First(ca => ca.AttributeType.FullName == "Xamarin.Forms.ParameterAttribute")
 						.ConstructorArguments.First()
 						.Value as string;
-				if (!node.Properties.ContainsKey(new XmlName("", propname)))
-				{
+				if (!node.Properties.ContainsKey(new XmlName("", propname))) {
 					missingArgName = propname;
 					return false;
 				}
@@ -219,8 +219,7 @@ namespace Xamarin.Forms.Xaml
 		{
 			object[] arguments = CreateArgumentsArray(node);
 
-			if (!node.Properties.ContainsKey(XmlName.xFactoryMethod))
-			{
+			if (!node.Properties.ContainsKey(XmlName.xFactoryMethod)) {
 				//non-default ctor
 				try {
 					return Activator.CreateInstance(nodeType, arguments);
@@ -232,7 +231,9 @@ namespace Xamarin.Forms.Xaml
 
 			var factoryMethod = ((string)((ValueNode)node.Properties[XmlName.xFactoryMethod]).Value);
 			Type[] types = arguments == null ? new Type[0] : arguments.Select(a => a.GetType()).ToArray();
-			Func<MethodInfo, bool> isMatch = m => {
+
+			bool isMatch(MethodInfo m)
+			{
 				if (m.Name != factoryMethod)
 					return false;
 				var p = m.GetParameters();
@@ -241,17 +242,18 @@ namespace Xamarin.Forms.Xaml
 				if (!m.IsStatic)
 					return false;
 				for (var i = 0; i < p.Length; i++) {
-					if ((p [i].ParameterType.IsAssignableFrom(types [i])))
+					if ((p[i].ParameterType.IsAssignableFrom(types[i])))
 						continue;
-					var op_impl =  p[i].ParameterType.GetImplicitConversionOperator(fromType: types[i], toType: p[i].ParameterType)
+					var op_impl = p[i].ParameterType.GetImplicitConversionOperator(fromType: types[i], toType: p[i].ParameterType)
 								?? types[i].GetImplicitConversionOperator(fromType: types[i], toType: p[i].ParameterType);
 
 					if (op_impl == null)
 						return false;
-					arguments [i] = op_impl.Invoke(null, new [] { arguments [i]});
+					arguments[i] = op_impl.Invoke(null, new[] { arguments[i] });
 				}
 				return true;
-			};
+			}
+
 			try {
 				var mi = nodeType.GetRuntimeMethods().FirstOrDefault(isMatch);
 				if (mi == null)
@@ -268,17 +270,13 @@ namespace Xamarin.Forms.Xaml
 			if (!enode.Properties.ContainsKey(XmlName.xArguments))
 				return null;
 			var node = enode.Properties[XmlName.xArguments];
-			var elementNode = node as ElementNode;
-			if (elementNode != null)
-			{
+			if (node is ElementNode elementNode) {
 				var array = new object[1];
 				array[0] = Values[elementNode];
 				return array;
 			}
 
-			var listnode = node as ListNode;
-			if (listnode != null)
-			{
+			if (node is ListNode listnode) {
 				var array = new object[listnode.CollectionItems.Count];
 				for (var i = 0; i < listnode.CollectionItems.Count; i++)
 					array[i] = Values[(ElementNode)listnode.CollectionItems[i]];
@@ -291,21 +289,15 @@ namespace Xamarin.Forms.Xaml
 		{
 			var n = ctorInfo.GetParameters().Length;
 			var array = new object[n];
-			for (var i = 0; i < n; i++)
-			{
+			for (var i = 0; i < n; i++) {
 				var parameter = ctorInfo.GetParameters()[i];
 				var propname =
 					parameter.CustomAttributes.First(attr => attr.AttributeType == typeof (ParameterAttribute))
 						.ConstructorArguments.First()
 						.Value as string;
 				var name = new XmlName("", propname);
-				INode node;
-				if (!enode.Properties.TryGetValue(name, out node))
-				{
-					throw new XamlParseException(
-						String.Format("The Property {0} is required to create a {1} object.", propname, ctorInfo.DeclaringType.FullName),
-						enode as IXmlLineInfo);
-				}
+				if (!enode.Properties.TryGetValue(name, out INode node))
+					throw new XamlParseException($"The Property {propname} is required to create a {ctorInfo.DeclaringType.FullName} object.", enode as IXmlLineInfo);
 				if (!enode.SkipProperties.Contains(name))
 					enode.SkipProperties.Add(name);
 				var value = Context.Values[node];
@@ -319,14 +311,11 @@ namespace Xamarin.Forms.Xaml
 			return array;
 		}
 
-		static bool IsXaml2009LanguagePrimitive(IElementNode node)
-		{
-			return node.NamespaceURI == XamlParser.X2009Uri;
-		}
+		static bool IsXaml2009LanguagePrimitive(IElementNode node) => node.NamespaceURI == XamlParser.X2009Uri;
 
 		static object CreateLanguagePrimitive(Type nodeType, IElementNode node)
 		{
-			object value = null;
+			object value;
 			if (nodeType == typeof (string))
 				value = String.Empty;
 			else if (nodeType == typeof (Uri))
@@ -334,95 +323,43 @@ namespace Xamarin.Forms.Xaml
 			else
 				value = Activator.CreateInstance(nodeType);
 
-			if (node.CollectionItems.Count == 1 && node.CollectionItems[0] is ValueNode &&
-			    ((ValueNode)node.CollectionItems[0]).Value is string)
-			{
-				var valuestring = ((ValueNode)node.CollectionItems[0]).Value as string;
-
-				if (nodeType == typeof(SByte)) {
-					sbyte retval;
-					if (sbyte.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Int16)) {
-					short retval;
-					if (short.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Int32)) {
-					int retval;
-					if (int.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Int64)) {
-					long retval;
-					if (long.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Byte)) {
-					byte retval;
-					if (byte.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(UInt16)) {
-					ushort retval;
-					if (ushort.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(UInt32)) {
-					uint retval;
-					if (uint.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(UInt64)) {
-					ulong retval;
-					if (ulong.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Single)) {
-					float retval;
-					if (float.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof(Double)) {
-					double retval;
-					if (double.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof (Boolean))
-				{
-					bool outbool;
-					if (bool.TryParse(valuestring, out outbool))
-						return outbool;
-				}
-				if (nodeType == typeof(TimeSpan)) {
-					TimeSpan retval;
-					if (TimeSpan.TryParse(valuestring, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-				if (nodeType == typeof (char))
-				{
-					char retval;
-					if (char.TryParse(valuestring, out retval))
-						return retval;
-				}
+			if (   node.CollectionItems.Count == 1
+				&& node.CollectionItems[0] is ValueNode
+				&& ((ValueNode)node.CollectionItems[0]).Value is string valuestring) {
+				if (nodeType == typeof(SByte) && sbyte.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var sbyteval))
+					return sbyteval;
+				if (nodeType == typeof(Int16) && short.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var int16val))
+					return int16val;
+				if (nodeType == typeof(Int32) && int.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var int32val))
+					return int32val;
+				if (nodeType == typeof(Int64) && long.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var int64val))
+					return int64val;
+				if (nodeType == typeof(Byte) && byte.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var byteval))
+					return byteval;
+				if (nodeType == typeof(UInt16) && ushort.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var uint16val))
+					return uint16val;
+				if (nodeType == typeof(UInt32) && uint.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var uint32val))
+					return uint32val;
+				if (nodeType == typeof(UInt64) && ulong.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var uint64val))
+					return uint64val;
+				if (nodeType == typeof(Single) && float.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var singleval))
+					return singleval;
+				if (nodeType == typeof(Double) && double.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var doubleval))
+					return doubleval;
+				if (nodeType == typeof(Boolean) && bool.TryParse(valuestring, out var boolval))
+					return boolval;
+				if (nodeType == typeof(TimeSpan) && TimeSpan.TryParse(valuestring, CultureInfo.InvariantCulture, out TimeSpan timespanval))
+					return timespanval;
+				if (nodeType == typeof(char) && char.TryParse(valuestring, out var charval))
+					return charval;
 				if (nodeType == typeof (string))
 					return valuestring;
-				if (nodeType == typeof (decimal))
-				{
-					decimal retval;
-					if (decimal.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out retval))
-						return retval;
-				}
-
-				else if (nodeType == typeof (Uri))
-				{
-					Uri retval;
-					if (Uri.TryCreate(valuestring, UriKind.RelativeOrAbsolute, out retval))
-						return retval;
-				}
+				if (nodeType == typeof(decimal) && decimal.TryParse(valuestring, NumberStyles.Number, CultureInfo.InvariantCulture, out var decimalval))
+					return decimalval;
+				if (nodeType == typeof(Uri) && Uri.TryCreate(valuestring, UriKind.RelativeOrAbsolute, out Uri urival))
+					return urival;
 			}
 			return value;
 		}
 	}
-}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Xaml/NamescopingVisitor.cs b/Xamarin.Forms.Xaml/NamescopingVisitor.cs
index 97e9fc707..5cde2cb7d 100644
--- a/Xamarin.Forms.Xaml/NamescopingVisitor.cs
+++ b/Xamarin.Forms.Xaml/NamescopingVisitor.cs
@@ -5,12 +5,11 @@ namespace Xamarin.Forms.Xaml
 {
 	class NamescopingVisitor : IXamlNodeVisitor
 	{
-		readonly Dictionary<INode, INameScope> _scopes = new Dictionary<INode, INameScope>();
+		readonly Dictionary<INode, NameScopeRef> _scopes = new Dictionary<INode, NameScopeRef>();
 
 		public NamescopingVisitor(HydrationContext context)
-			=> Values = context.Values;
-
-		Dictionary<INode, object> Values { get; set; }
+		{
+		}
 
 		public TreeVisitingMode VisitingMode => TreeVisitingMode.TopDown;
 		public bool StopOnDataTemplate => false;
@@ -19,37 +18,29 @@ namespace Xamarin.Forms.Xaml
 		public bool SkipChildren(INode node, INode parentNode) => false;
 		public bool IsResourceDictionary(ElementNode node) => false;
 
-		public void Visit(ValueNode node, INode parentNode)
-			=> _scopes[node] = _scopes[parentNode];
-
-		public void Visit(MarkupNode node, INode parentNode)
-			=> _scopes[node] = _scopes[parentNode];
+		public void Visit(ValueNode node, INode parentNode) => _scopes[node] = _scopes[parentNode];
+		public void Visit(MarkupNode node, INode parentNode) => _scopes[node] = _scopes[parentNode];
 
 		public void Visit(ElementNode node, INode parentNode)
-			=> _scopes[node] = node.Namescope = (parentNode == null || IsDataTemplate(node, parentNode) || IsStyle(node, parentNode) || IsVisualStateGroupList(node))
-								   ? new NameScope()
+			=> _scopes[node] = node.NameScopeRef = (parentNode == null || IsDataTemplate(node, parentNode) || IsStyle(node, parentNode) || IsVisualStateGroupList(node))
+								   ? new NameScopeRef { NameScope = new NameScope() }
 								   : _scopes[parentNode];
 
-		public void Visit(RootNode node, INode parentNode)
-			=> _scopes[node] = node.Namescope = new NameScope();
+		public void Visit(RootNode node, INode parentNode) => _scopes[node] = node.NameScopeRef = new NameScopeRef { NameScope = new NameScope() };
 
 		public void Visit(ListNode node, INode parentNode) =>
 			_scopes[node] = _scopes[parentNode];
 
 		static bool IsDataTemplate(INode node, INode parentNode)
 		{
-			var parentElement = parentNode as IElementNode;
-			if (   parentElement != null
-			    && parentElement.Properties.TryGetValue(XmlName._CreateContent, out var createContent)
-			    && createContent == node)
+			if (   parentNode is IElementNode parentElement
+				&& parentElement.Properties.TryGetValue(XmlName._CreateContent, out var createContent)
+				&& createContent == node)
 				return true;
 			return false;
 		}
 
-		static bool IsStyle(INode node, INode parentNode)
-			=> (parentNode as ElementNode)?.XmlType.Name == "Style";
-
-		static bool IsVisualStateGroupList(ElementNode node)
-			=> node?.XmlType.Name == "VisualStateGroup" && node?.Parent is IListNode;
+		static bool IsStyle(INode node, INode parentNode) => (parentNode as ElementNode)?.XmlType.Name == "Style";
+		static bool IsVisualStateGroupList(ElementNode node) => node?.XmlType.Name == "VisualStateGroup" && node?.Parent is IListNode;
 	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Xaml/RegisterXNamesVisitor.cs b/Xamarin.Forms.Xaml/RegisterXNamesVisitor.cs
index 7d70da589..881b1aba1 100644
--- a/Xamarin.Forms.Xaml/RegisterXNamesVisitor.cs
+++ b/Xamarin.Forms.Xaml/RegisterXNamesVisitor.cs
@@ -1,11 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Globalization;
-using System.Linq;
-using System.Reflection;
-using System.Xml;
 using Xamarin.Forms.Internals;
-using Xamarin.Forms.Xaml.Internals;
 
 namespace Xamarin.Forms.Xaml
 {
@@ -32,7 +27,7 @@ namespace Xamarin.Forms.Xaml
 				return;
 
 			try {
-				((IElementNode)parentNode).Namescope.RegisterName((string)node.Value, Values[parentNode]);
+				((IElementNode)parentNode).NameScopeRef.NameScope.RegisterName((string)node.Value, Values[parentNode]);
 			}
 			catch (ArgumentException ae) {
 				if (ae.ParamName != "name")
@@ -73,12 +68,6 @@ namespace Xamarin.Forms.Xaml
 		}
 
 		static bool IsXNameProperty(ValueNode node, INode parentNode)
-		{
-			var parentElement = parentNode as IElementNode;
-			INode xNameNode;
-			if (parentElement != null && parentElement.Properties.TryGetValue(XmlName.xName, out xNameNode) && xNameNode == node)
-				return true;
-			return false;
-		}
+			=> parentNode is IElementNode parentElement && parentElement.Properties.TryGetValue(XmlName.xName, out INode xNameNode) && xNameNode == node;
 	}
 }
diff --git a/Xamarin.Forms.Xaml/XamlNode.cs b/Xamarin.Forms.Xaml/XamlNode.cs
index e5b536cb2..a6eea39c4 100644
--- a/Xamarin.Forms.Xaml/XamlNode.cs
+++ b/Xamarin.Forms.Xaml/XamlNode.cs
@@ -24,7 +24,7 @@ namespace Xamarin.Forms.Xaml
 	{
 		Dictionary<XmlName, INode> Properties { get; }
 		List<XmlName> SkipProperties { get; }
-		INameScope Namescope { get; }
+		NameScopeRef NameScopeRef { get; }
 		XmlType XmlType { get; }
 		string NamespaceURI { get; }
 	}
@@ -34,6 +34,11 @@ namespace Xamarin.Forms.Xaml
 		List<INode> CollectionItems { get; }
 	}
 
+	class NameScopeRef
+	{
+		public INameScope NameScope { get; set; }
+	}
+
 	[DebuggerDisplay("{NamespaceUri}:{Name}")]
 	class XmlType
 	{
@@ -112,6 +117,7 @@ namespace Xamarin.Forms.Xaml
 		};
 	}
 
+
 	[DebuggerDisplay("{XmlType.Name}")]
 	class ElementNode : BaseNode, IValueNode, IElementNode
 	{
@@ -131,7 +137,7 @@ namespace Xamarin.Forms.Xaml
 		public List<INode> CollectionItems { get; }
 		public XmlType XmlType { get; }
 		public string NamespaceURI { get; }
-		public INameScope Namescope { get; set; }
+		public NameScopeRef NameScopeRef { get; set; }
 
 		public override void Accept(IXamlNodeVisitor visitor, INode parentNode)
 		{
@@ -152,10 +158,8 @@ namespace Xamarin.Forms.Xaml
 
 		bool IsDataTemplate(INode parentNode)
 		{
-			var parentElement = parentNode as IElementNode;
-			INode createContent;
-			if (parentElement != null &&
-				parentElement.Properties.TryGetValue(XmlName._CreateContent, out createContent) &&
+			if (parentNode is IElementNode parentElement &&
+				parentElement.Properties.TryGetValue(XmlName._CreateContent, out INode createContent) &&
 				createContent == this)
 				return true;
 			return false;
diff --git a/Xamarin.Forms.Xaml/XamlServiceProvider.cs b/Xamarin.Forms.Xaml/XamlServiceProvider.cs
index 518502473..b6d2000b1 100644
--- a/Xamarin.Forms.Xaml/XamlServiceProvider.cs
+++ b/Xamarin.Forms.Xaml/XamlServiceProvider.cs
@@ -74,16 +74,9 @@ namespace Xamarin.Forms.Xaml.Internals
 			set { services[typeof (IValueConverterProvider)] = value; }
 		}
 
-		public object GetService(Type serviceType)
-		{
-			object service;
-			return services.TryGetValue(serviceType, out service) ? service : null;
-		}
+		public object GetService(Type serviceType) => services.TryGetValue(serviceType, out var service) ? service : null;
 
-		public void Add(Type type, object service)
-		{
-			services.Add(type, service);
-		}
+		public void Add(Type type, object service) => services.Add(type, service);
 	}
 
 	class XamlValueTargetProvider : IProvideParentValues, IProvideValueTarget
@@ -104,21 +97,16 @@ namespace Xamarin.Forms.Xaml.Internals
 
 		IEnumerable<object> IProvideParentValues.ParentObjects
 		{
-			get
-			{
+			get {
 				if (Node == null || Context == null)
 					yield break;
 				var n = Node;
-				object obj = null;
 				var context = Context;
-				while (n.Parent != null && context != null)
-				{
-					if (n.Parent is IElementNode)
-					{
-						if (context.Values.TryGetValue(n.Parent, out obj))
+				while (n.Parent != null && context != null) {
+					if (n.Parent is IElementNode) {
+						if (context.Values.TryGetValue(n.Parent, out var obj))
 							yield return obj;
-						else
-						{
+						else {
 							context = context.ParentContext;
 							continue;
 						}
@@ -159,14 +147,9 @@ namespace Xamarin.Forms.Xaml.Internals
 			this.scope = scope;
 		}
 
-		IEnumerable<object> IProvideParentValues.ParentObjects
-			=> objectAndParents;
-
-		object IProvideValueTarget.TargetObject
-			=> objectAndParents[0];
-
-		object IProvideValueTarget.TargetProperty
-			=> targetProperty;
+		IEnumerable<object> IProvideParentValues.ParentObjects => objectAndParents;
+		object IProvideValueTarget.TargetObject => objectAndParents[0];
+		object IProvideValueTarget.TargetProperty => targetProperty;
 
 		public object FindByName(string name)
 		{
@@ -277,15 +260,14 @@ namespace Xamarin.Forms.Xaml.Internals
 	class ReferenceProvider : IReferenceProvider
 	{
 		readonly INode _node;
-		internal ReferenceProvider(INode node)
-			=> _node = node;
+		internal ReferenceProvider(INode node) => _node = node;
 
 		public object FindByName(string name)
 		{
 			var n = _node;
-			object value = null;
 			while (n != null) {
-				if ((value = (n as IElementNode)?.Namescope?.FindByName(name)) != null)
+				object value;
+				if ((value = (n as IElementNode)?.NameScopeRef.NameScope?.FindByName(name)) != null)
 					return value;
 				n = n.Parent;
 			}
@@ -304,27 +286,16 @@ namespace Xamarin.Forms.Xaml.Internals
 	{
 		readonly Dictionary<string, string> namespaces = new Dictionary<string, string>();
 
-		public IDictionary<string, string> GetNamespacesInScope(XmlNamespaceScope scope)
-		{
-			throw new NotImplementedException();
-		}
+		public IDictionary<string, string> GetNamespacesInScope(XmlNamespaceScope scope) => throw new NotImplementedException();
 
 		public string LookupNamespace(string prefix)
 		{
-			string result;
-			if (namespaces.TryGetValue(prefix, out result))
+			if (namespaces.TryGetValue(prefix, out var result))
 				return result;
 			return null;
 		}
 
-		public string LookupPrefix(string namespaceName)
-		{
-			throw new NotImplementedException();
-		}
-
-		public void Add(string prefix, string ns)
-		{
-			namespaces.Add(prefix, ns);
-		}
+		public string LookupPrefix(string namespaceName) => throw new NotImplementedException();
+		public void Add(string prefix, string ns) => namespaces.Add(prefix, ns);
 	}
 }
\ No newline at end of file