Add first unit tests

Refactor code to be more easy to test
2018-12-26 12:57:38 +01:00 · 2018-12-26 12:57:38 +01:00 · aaca2c1893
--- a/XAMLator.Client/DocumentParser.cs
+++ b/XAMLator.Client/DocumentParser.cs
@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
@ -20,32 +21,48 @@ namespace XAMLator.Client
 																		  string text,
 																		  SyntaxTree syntaxTree,
 																		  SemanticModel semanticModel)
-		{
+		{
+			XAMLDocument xamlDocument = null;
+			FormsViewClassDeclaration xamlClass = null;
+			bool created;
+
 			// FIXME: Support any kind of types, not just Xamarin.Forms views
 			if (!fileName.EndsWith(".xaml") && !fileName.EndsWith(".xaml.cs"))
 			{
 				return null;
 			}

-			if (!GetOrCreate(fileName, text, syntaxTree, semanticModel,
-							 out FormsViewClassDeclaration xamlClass,
-							 out XAMLDocument xamlDocument))
+			// Check if we have already an instance of the class declaration for that file
+			if (!FormsViewClassDeclaration.TryGetByFileName(fileName, out xamlClass))
+			{
+				if (fileName.EndsWith(".xaml"))
+				{
+					xamlDocument = XAMLDocument.Parse(fileName, text);
+					// Check if we have an instance of class by namespace
+					if (!FormsViewClassDeclaration.TryGetByFullNamespace(xamlDocument.Type, out xamlClass))
+					{
+						xamlClass = await CreateFromXaml(xamlDocument);
+					}
+				}
+				else
+				{
+					xamlClass = await CreateFromCodeBehind(fileName, syntaxTree, semanticModel);
+				}
+			}
+
+			if (xamlClass == null)
 			{
-				Log.Error("Could not handle document update");
 				return null;
 			}

 			// The document is a XAML file
-			if (fileName.EndsWith(".xaml"))
+			if (fileName.EndsWith(".xaml") && xamlDocument == null)
 			{
-				if (xamlDocument == null)
-				{
-					xamlDocument = XAMLDocument.Parse(fileName, text);
-				}
+				xamlDocument = XAMLDocument.Parse(fileName, text);
 				await xamlClass.UpdateXaml(xamlDocument);
 			}
 			// The document is code behind
-			else if (fileName.EndsWith(".xaml.cs"))
+			if (fileName.EndsWith(".xaml.cs"))
 			{
 				var classDeclaration = FormsViewClassDeclaration.FindClass(syntaxTree, xamlClass.ClassName);
 				if (xamlClass.NeedsClassInitialization)
@ -55,78 +72,48 @@ namespace XAMLator.Client
 				xamlClass.UpdateCode(classDeclaration);
 			}
 			return xamlClass;
+		}
+
+		static async Task<FormsViewClassDeclaration> CreateFromXaml(XAMLDocument xamlDocument)
+
+		{
+			string codeBehindFilePath = xamlDocument.FilePath + ".cs";
+			if (!File.Exists(codeBehindFilePath))
+			{
+				Log.Error("XAML file without code behind");
+				return null;
+			}
+			var xamlClass = new FormsViewClassDeclaration(codeBehindFilePath, xamlDocument);
+			await xamlClass.UpdateXaml(xamlDocument);
+			return xamlClass;
 		}

+		static async Task<FormsViewClassDeclaration> CreateFromCodeBehind(string fileName,
+			SyntaxTree syntaxTree, SemanticModel semanticModel)

-		static bool GetOrCreate(string fileName,
-								string text,
-								SyntaxTree syntaxTree,
-								SemanticModel semanticModel,
-								out FormsViewClassDeclaration xamlClass,
-								out XAMLDocument xamlDocument)
 		{
-			string xaml = null, xamlFilePath = null, codeBehindFilePath = null;
-			xamlDocument = null;
+			string xaml = null, xamlFilePath = null, codeBehindFilePath = null;
+			XAMLDocument xamlDocument;

-			// Check if we have already an instance of the class declaration for that file
-			if (FormsViewClassDeclaration.TryGetByFileName(fileName, out xamlClass))
+			codeBehindFilePath = fileName;
+			var xamlCandidate = fileName.Substring(0, fileName.Length - 3);
+			if (File.Exists(xamlCandidate))
 			{
-				return true;
-			}
-
-			if (fileName.EndsWith(".xaml"))
-			{
-				xaml = text;
-				xamlFilePath = fileName;
-				var candidate = xamlFilePath + ".cs";
-				if (File.Exists(candidate))
-				{
-					codeBehindFilePath = candidate;
-				}
-			}
-			else
-			{
-				codeBehindFilePath = fileName;
-				var candidate = fileName.Substring(0, fileName.Length - 3);
-				if (File.Exists(candidate))
-				{
-					xamlFilePath = candidate;
-					xaml = File.ReadAllText(xamlFilePath);
-				}
+				xamlFilePath = xamlCandidate;
+				xaml = File.ReadAllText(xamlFilePath);
 			}

 			// FIXME: Handle XF views without XAML
 			// Parse the XAML file 
 			xamlDocument = XAMLDocument.Parse(xamlFilePath, xaml);
-			if (xamlDocument == null)
-			{
-				Log.Error("Error parsing XAML");
-				return false;
-			}

-			// Check if we have an instance of class by namespace
-			if (FormsViewClassDeclaration.TryGetByFullNamespace(xamlDocument.Type, out xamlClass))
-			{
-				return true;
-			}
+			var className = xamlDocument.Type.Split('.').Last();
+			var classDeclaration = FormsViewClassDeclaration.FindClass(syntaxTree, className);
+			var xamlClass = new FormsViewClassDeclaration(classDeclaration, semanticModel,
+													codeBehindFilePath, xamlDocument);

-			// This is the first time we have an update for this type
-
-			// Create a new class declaration instance from the syntax tree
-			if (syntaxTree != null)
-			{
-				var className = xamlDocument.Type.Split('.').Last();
-				var classDeclaration = FormsViewClassDeclaration.FindClass(syntaxTree, className);
-				xamlClass = new FormsViewClassDeclaration(classDeclaration, semanticModel,
-													 codeBehindFilePath, xamlDocument);
-			}
-			// Create a new class declaration instance from the XAML
-			else
-			{
-				xamlClass = new FormsViewClassDeclaration(codeBehindFilePath, xamlDocument);
-
-			}
-			return true;
+			await xamlClass.UpdateXaml(xamlDocument);
+			return xamlClass;
 		}
 	}
 }
--- a/XAMLator.Client/FormsViewClassDeclaration.cs
+++ b/XAMLator.Client/FormsViewClassDeclaration.cs
@ -28,7 +28,15 @@ namespace XAMLator.Client
 		/// <summary>
 		/// The xaml classes.
 		/// </summary>
-		static readonly List<FormsViewClassDeclaration> classesCache = new List<FormsViewClassDeclaration>();
+		internal static readonly List<FormsViewClassDeclaration> classesCache = new List<FormsViewClassDeclaration>();
+
+		/// <summary>
+		/// Reset the cache.
+		/// </summary>
+		public static void Reset()
+		{
+			classesCache.Clear();
+		}

 		/// <summary>
 		/// Tries to find a cached class declaration with the same full namespace.
@ -91,7 +99,6 @@ namespace XAMLator.Client
 			this.xamlFilePath = xaml.FilePath;
 			StyleSheets = new Dictionary<string, string>();
 			FillClassInfo(classDeclarationSyntax, model);
-			UpdateXaml(xaml);
 			UpdateCode(classDeclarationSyntax);
 			classesCache.Add(this);
 		}
@ -110,7 +117,6 @@ namespace XAMLator.Client
 			Namespace = xaml.Type.Substring(0, xaml.Type.LastIndexOf('.'));
 			ClassName = xaml.Type.Split('.').Last();
 			classesCache.Add(this);
-			UpdateXaml(xaml);
 		}

 		/// <summary>
@ -203,6 +209,10 @@ namespace XAMLator.Client
 		/// <param name="xaml">Xaml.</param>
 		internal async Task UpdateXaml(XAMLDocument xaml)
 		{
+			if (Xaml == xaml.XAML)
+			{
+				return;
+			}
 			Xaml = xaml.XAML;
 			LoadStyleSheets(xaml);
 			await UpdateAutoGeneratedCodeBehind();
@ -324,9 +334,7 @@ namespace XAMLator.Client
 		void FillPartials()
 		{
 			partials = symbol.Locations
-							 .Where(l =>
-									l.SourceTree.FilePath != codeBehindFilePath &&
-									l.SourceTree.FilePath != autoGenCodeBehindFilePath)
+							 .Where(FileIsPartial)
 							 .SelectMany(l => FindClass(l.SourceTree, classDeclarationSyntax.Identifier.Text).Members)
 							 .ToList();
 		}
@ -432,7 +440,7 @@ namespace XAMLator.Client
 		/// Rewrites the autogenerated code constructor replace the LoadFromXaml
 		/// call that reads the XAML fro the assembly resources for a call to
 		/// <see cref="XAMLator.Server.VM.LoadXaml"/> that loads the XAML from
-		/// the <see cref="EvalRequest"/>
+		/// the <see cref="EvalRequestMessage"/>
 		/// </summary>
 		/// <returns>The autogenerated code constructor.</returns>
 		/// <param name="classDeclaration">Class declaration.</param>
@ -453,6 +461,13 @@ namespace XAMLator.Client
 			return classDeclaration.ReplaceNode(loadFromXaml, newLoadXaml);
 		}

+		bool FileIsPartial(Location location)
+		{
+
+			return location.SourceTree.FilePath != codeBehindFilePath &&
+				location.SourceTree.FilePath != autoGenCodeBehindFilePath;
+		}
+
 		/// <summary>
 		/// Finds a class for the given name in a syntax tree.
 		/// </summary>
--- a/XAMLator.Client/XAMLDocument.cs
+++ b/XAMLator.Client/XAMLDocument.cs
@ -27,33 +27,25 @@ namespace XAMLator

 		public static XAMLDocument Parse(string filePath, string xaml)
 		{
-			try
+			using (var stream = new StringReader(xaml))
 			{
-				using (var stream = new StringReader(xaml))
-				{
-					var reader = XmlReader.Create(stream);
-					var xdoc = XDocument.Load(reader);
-					XNamespace x = "http://schemas.microsoft.com/winfx/2009/xaml";
-					XNamespace xm = "http://xamarin.com/schemas/2014/forms";
-					var classAttribute = xdoc.Root.Attribute(x + "Class");
-					CleanAutomationIds(xdoc.Root);
-					var styleSheetElements = xdoc.Root
-												 .Descendants()
-												 .Where(e => e.Name.ToString().EndsWith("StyleSheet"));
-					CleanStyleSheets(styleSheetElements);
-					var styleSheets = styleSheetElements
-						.Select(e => e.Attribute("Source"))
-						.Where(e => e != null)
-						.Select(e => e.Value)
-						.ToList();
-					xaml = xdoc.ToString();
-					return new XAMLDocument(filePath, xaml, classAttribute.Value, styleSheets);
-				}
-			}
-			catch (Exception ex)
-			{
-				Log.Exception(ex);
-				return null;
+				var reader = XmlReader.Create(stream);
+				var xdoc = XDocument.Load(reader);
+				XNamespace x = "http://schemas.microsoft.com/winfx/2009/xaml";
+				XNamespace xm = "http://xamarin.com/schemas/2014/forms";
+				var classAttribute = xdoc.Root.Attribute(x + "Class");
+				CleanAutomationIds(xdoc.Root);
+				var styleSheetElements = xdoc.Root
+											 .Descendants()
+											 .Where(e => e.Name.ToString().EndsWith("StyleSheet"));
+				CleanStyleSheets(styleSheetElements);
+				var styleSheets = styleSheetElements
+					.Select(e => e.Attribute("Source"))
+					.Where(e => e != null)
+					.Select(e => e.Value)
+					.ToList();
+				xaml = xdoc.ToString();
+				return new XAMLDocument(filePath, xaml, classAttribute.Value, styleSheets);
 			}
 		}

--- a/XAMLator.Client/XAMLator.cs
+++ b/XAMLator.Client/XAMLator.cs
@ -4,7 +4,7 @@ namespace XAMLator.Client
 {
 	public class XAMLatorMonitor
 	{
-		TcpCommunicatorServer server;
+		ITcpCommunicatorServer server;

 		public static XAMLatorMonitor Init(IIDE ide)
 		{
@ -14,19 +14,28 @@ namespace XAMLator.Client

 		public static XAMLatorMonitor Instance { get; private set; }

-		XAMLatorMonitor(IIDE ide)
+		internal XAMLatorMonitor(IIDE ide, ITcpCommunicatorServer server = null)
 		{
 			IDE = ide;
-			server = new TcpCommunicatorServer(Constants.DEFAULT_PORT);
+			if (server == null)
+			{
+				server = new TcpCommunicatorServer();
+			}
+			this.server = server;
 			ide.DocumentChanged += HandleDocumentChanged;
 		}

 		public IIDE IDE { get; private set; }

 		public void StartMonitoring()
+		{
+			StartMonitoring(Constants.DEFAULT_PORT);
+		}
+
+		internal void StartMonitoring(int port)
 		{
 			IDE.MonitorEditorChanges();
-			server.StartListening();
+			server.StartListening(port);
 		}

 		async void HandleDocumentChanged(object sender, DocumentChangedEventArgs e)
@ -36,25 +45,33 @@ namespace XAMLator.Client
 				return;
 			}

-			var classDecl = await DocumentParser.ParseDocument(e.Filename, e.Text, e.SyntaxTree, e.SemanticModel);
-
-			if (classDecl == null)
+			try
 			{
-				return;
+				var classDecl = await DocumentParser.ParseDocument(e.Filename, e.Text, e.SyntaxTree, e.SemanticModel);
+
+				if (classDecl == null)
+				{
+					return;
+				}
+
+				EvalRequestMessage request = new EvalRequestMessage
+				{
+					Declarations = classDecl.Code,
+					NeedsRebuild = classDecl.NeedsRebuild,
+					OriginalTypeName = classDecl.FullNamespace,
+					NewTypeName = classDecl.CurrentFullNamespace,
+					Xaml = classDecl.Xaml,
+					XamlResourceName = classDecl.XamlResourceId,
+					StyleSheets = classDecl.StyleSheets
+				};
+				await server.Send(request);
 			}
-
-			EvalRequest request = new EvalRequest
+			catch (Exception ex)
 			{
-				Declarations = classDecl.Code,
-				NeedsRebuild = classDecl.NeedsRebuild,
-				OriginalTypeName = classDecl.FullNamespace,
-				NewTypeName = classDecl.CurrentFullNamespace,
-				Xaml = classDecl.Xaml,
-				XamlResourceName = classDecl.XamlResourceId,
-				StyleSheets = classDecl.StyleSheets
-			};
-
-			await server.Send(request);
+				Log.Exception(ex);
+				await server.Send(new ErrorMessage($"Error parsing {e.Filename}",
+					ex.ToString()));
+			}
 		}
 	}
 }
--- a/XAMLator.Core/EvalRequest.cs
+++ b/XAMLator.Core/EvalRequest.cs
@ -5,7 +5,25 @@ using System.ComponentModel;

 namespace XAMLator
 {
-	public class EvalRequest
+	public class Message
+	{
+		public string Type => GetType().Name;
+	}
+
+	public class ErrorMessage : Message
+	{
+		public ErrorMessage(string title, string exception)
+		{
+			Title = title;
+			Exception = exception;
+		}
+
+		public string Title { get; }
+
+		public string Exception { get; }
+	}
+
+	public class EvalRequestMessage : Message
 	{
 		public string Declarations;
 		public string NewTypeName;
--- a/XAMLator.Core/ITcpCommunicator.cs
+++ b/XAMLator.Core/ITcpCommunicator.cs
@ -0,0 +1,12 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator
+{
+	public interface ITcpCommunicator
+	{
+		event EventHandler<object> DataReceived;
+
+		Task<bool> Send<T>(T obj);
+	}
+}
--- a/XAMLator.Core/ITcpCommunicatorClient.cs
+++ b/XAMLator.Core/ITcpCommunicatorClient.cs
@ -0,0 +1,11 @@
+using System.Threading.Tasks;
+
+namespace XAMLator
+{
+	public interface ITcpCommunicatorClient : ITcpCommunicator
+	{
+		Task<bool> Connect(string ip, int port);
+
+		void Disconnect();
+	}
+}
--- a/XAMLator.Core/ITcpCommunicatorServer.cs
+++ b/XAMLator.Core/ITcpCommunicatorServer.cs
@ -0,0 +1,16 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator
+{
+	public interface ITcpCommunicatorServer : ITcpCommunicator
+	{
+		event EventHandler ClientConnected;
+
+		int ClientsCount { get; }
+
+		Task<bool> StartListening(int serverPort);
+
+		void StopListening();
+	}
+}
--- a/XAMLator.Core/IUIToolkit.cs
+++ b/XAMLator.Core/IUIToolkit.cs
@ -0,0 +1,12 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator
+{
+	public interface IUIToolkit
+	{
+		Task RunInUIThreadAsync(Func<Task> action);
+
+		void RunInUIThread(Action action);
+	}
+}
--- a/XAMLator.Core/TcpCommunicator.cs
+++ b/XAMLator.Core/TcpCommunicator.cs
@ -8,22 +8,18 @@ using System.Threading.Tasks;

 namespace XAMLator
 {
-	public class TcpCommunicatorServer : TcpCommunicator
+	public class TcpCommunicatorServer : TcpCommunicator, ITcpCommunicatorServer
 	{
 		int serverPort;
 		TcpListener listener;

 		public event EventHandler ClientConnected;

-		public TcpCommunicatorServer(int serverPort)
-		{
-			this.serverPort = serverPort;
-		}
-
 		public int ClientsCount => clients.Count;

-		public Task<bool> StartListening()
+		public Task<bool> StartListening(int serverPort)
 		{
+			this.serverPort = serverPort;
 			var taskCompletion = new TaskCompletionSource<bool>();
 			Task.Factory.StartNew(() => Run(taskCompletion), TaskCreationOptions.LongRunning);
 			return taskCompletion.Task;
@ -68,7 +64,7 @@ namespace XAMLator
 		}
 	}

-	public class TcpCommunicatorClient : TcpCommunicator
+	public class TcpCommunicatorClient : TcpCommunicator, ITcpCommunicatorClient
 	{
 		TcpClient client;

@ -89,7 +85,7 @@ namespace XAMLator
 		}
 	}

-	public abstract class TcpCommunicator
+	public abstract class TcpCommunicator : ITcpCommunicator
 	{
 		string pendingmsg;
 		protected ConcurrentDictionary<Guid, Tuple<TcpClient, CancellationTokenSource>> clients = new ConcurrentDictionary<Guid, Tuple<TcpClient, CancellationTokenSource>>();
--- a/XAMLator.Core/XAMLator.Core.projitems
+++ b/XAMLator.Core/XAMLator.Core.projitems
@ -17,5 +17,9 @@
    <Compile Include="$(MSBuildThisFileDirectory)ExtensionMethods.cs" />
    <Compile Include="$(MSBuildThisFileDirectory)NetworkUtils.cs" />
    <Compile Include="$(MSBuildThisFileDirectory)TcpCommunicator.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)ITcpCommunicatorServer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)ITcpCommunicator.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)ITcpCommunicatorClient.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)IUIToolkit.cs" />
  </ItemGroup>
 </Project>
--- a/XAMLator.Server.Shared/AssemblyInfo.cs
+++ b/XAMLator.Server.Shared/AssemblyInfo.cs
@ -0,0 +1,4 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("XAMLator.Server.Tests")]
+
--- a/XAMLator.Server.Shared/ErrorViewModel.cs
+++ b/XAMLator.Server.Shared/ErrorViewModel.cs
@ -44,10 +44,15 @@ namespace XAMLator.Server
 			}
 		}

+		public void SetError(string title, string ex)
+		{
+			Error = ex;
+			Title = title;
+		}
+
 		public void SetError(string title, Exception ex)
 		{
-			Error = ex.ToString();
-			Title = title;
+			SetError(title, ex.ToString());
 		}

 		public void SetError(string title, EvalResult result)
--- a/XAMLator.Server.Shared/IEvaluator.cs
+++ b/XAMLator.Server.Shared/IEvaluator.cs
@ -10,7 +10,7 @@ namespace XAMLator.Server
 		/// <returns>True if succeeded.</returns>
 		/// <param name="code">The class code.</param>
 		/// <param name="result">Eval result.</param>
-		Task<bool> EvaluateCode(string code, EvalResult result);
+		Task<bool> EvaluateCode(string code, EvalResult result, string extraCode = null);

 		/// <summary>
 		/// Check if evaluation is supported. This can fail in iOS real devices
--- a/XAMLator.Server.Shared/MonoEvaluator.cs
+++ b/XAMLator.Server.Shared/MonoEvaluator.cs
@ -30,7 +30,7 @@ namespace XAMLator.Server

 		public bool IsEvaluationSupported => isEvaluationSupported;

-		public Task<bool> EvaluateCode(string code, EvalResult result)
+		public Task<bool> EvaluateCode(string code, EvalResult result, string initCode = null)
 		{
 			if (string.IsNullOrEmpty(code))
 			{
@ -42,8 +42,11 @@ namespace XAMLator.Server
 			try
 			{
 				printer.Reset();
-				eval.Evaluate(code, out object retResult, out bool result_set);
-				result.Result = retResult;
+				if (initCode != null)
+				{
+					eval.Evaluate(initCode, out object retResult, out bool result_set);
+				}
+				result.Result = eval.Evaluate(code);
 				return Task.FromResult(true);
 			}
 			catch (Exception ex)
--- a/XAMLator.Server.Shared/PreviewServer.cs
+++ b/XAMLator.Server.Shared/PreviewServer.cs
@ -1,9 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Net;
-using System.Reflection;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Newtonsoft.Json.Linq;
@ -22,32 +19,41 @@ namespace XAMLator.Server
 		TaskScheduler mainScheduler;
 		IPreviewer previewer;
 		bool isRunning;
-		TcpCommunicatorClient client;
+		ITcpCommunicatorClient client;
 		ErrorViewModel errorViewModel;
+		IUIToolkit uiToolkit;

 		internal static PreviewServer Instance => serverInstance;

-		PreviewServer()
+		internal PreviewServer()
 		{
-			client = new TcpCommunicatorClient();
-			client.DataReceived += HandleDataReceived;
 			errorViewModel = new ErrorViewModel();
 		}

 		public static Task<bool> Run(Dictionary<Type, object> viewModelsMapping = null,
 			IPreviewer previewer = null, string ideIP = null, int idePort = Constants.DEFAULT_PORT)
 		{
-			return Instance.RunInternal(viewModelsMapping, previewer, ideIP, idePort);
+			return Instance.RunInternal(viewModelsMapping, previewer, ideIP, idePort,
+				new UIToolkit(), new TcpCommunicatorClient());
 		}

 		internal async Task<bool> RunInternal(Dictionary<Type, object> viewModelsMapping,
-			IPreviewer previewer, string ideIP, int idePort)
+			IPreviewer previewer, string ideIP, int idePort, IUIToolkit uiToolkit, ITcpCommunicatorClient client)
 		{
 			if (isRunning)
 			{
 				return true;
 			}

+			this.uiToolkit = uiToolkit;
+
+			if (client == null)
+			{
+				client = new TcpCommunicatorClient();
+			}
+			this.client = client;
+			client.DataReceived += HandleDataReceived;
+
 			mainScheduler = TaskScheduler.FromCurrentSynchronizationContext();
 			await RegisterDevice(ideIP, idePort);
 			if (viewModelsMapping == null)
@ -98,38 +104,49 @@ namespace XAMLator.Server

 		async void HandleDataReceived(object sender, object e)
 		{
-			await HandleEvalRequest((e as JContainer).ToObject<EvalRequest>());
+			var container = e as JContainer;
+			string type = (string)container["Type"];
+
+			if (type == typeof(EvalRequestMessage).Name)
+			{
+				await HandleEvalRequest(container.ToObject<EvalRequestMessage>());
+			}
+			else if (type == typeof(ErrorMessage).Name)
+			{
+				var errorMessage = container.ToObject<ErrorMessage>();
+				await uiToolkit.RunInUIThreadAsync(async () =>
+				{
+					errorViewModel.SetError("Oh no! An exception!", errorMessage.Exception);
+					await previewer.NotifyError(errorViewModel);
+				});
+			}
 		}

-		async Task HandleEvalRequest(EvalRequest request)
+		async Task HandleEvalRequest(EvalRequestMessage request)
 		{
 			EvalResponse evalResponse = new EvalResponse();
 			EvalResult result;
 			try
 			{
 				result = await vm.Eval(request, mainScheduler, CancellationToken.None);
-				if (result.ResultType != null)
+				if (result.HasResult || result.ResultType != null)
 				{
-					var tcs = new TaskCompletionSource<bool>();
-					Xamarin.Forms.Device.BeginInvokeOnMainThread(async () =>
-					{
-						try
-						{
-							await previewer.Preview(result);
-							tcs.SetResult(true);
-						}
-						catch (Exception ex)
-						{
-							errorViewModel.SetError("Oh no! An exception!", ex);
-							await previewer.NotifyError(errorViewModel);
-							tcs.SetException(ex);
-						}
-					});
-					await tcs.Task;
+					await uiToolkit.RunInUIThreadAsync(async () =>
+					   {
+						   try
+						   {
+							   await previewer.Preview(result);
+						   }
+						   catch (Exception ex)
+						   {
+							   errorViewModel.SetError("Oh no! An exception!", ex);
+							   await previewer.NotifyError(errorViewModel);
+						   }
+					   });
 				}
 				else
 				{
-					Xamarin.Forms.Device.BeginInvokeOnMainThread(async () =>
+					await uiToolkit.RunInUIThreadAsync(async () =>
 					{
 						errorViewModel.SetError("Oh no! An evaluation error!", result);
 						await previewer.NotifyError(errorViewModel);
--- a/XAMLator.Server.Shared/Previewer.cs
+++ b/XAMLator.Server.Shared/Previewer.cs
@ -44,6 +44,34 @@ namespace XAMLator.Server
 		{
 			Log.Information($"Visualizing result {res.ResultType}");

+			Page page = CreateViewFromResult(res);
+			if (page != null)
+			{
+				await PreviewPage(page);
+			}
+		}
+
+		public virtual async Task NotifyError(ErrorViewModel errorViewModel)
+		{
+			await EnsurePresented();
+			errorViewModel.CloseCommand = closeCommand;
+			errorPage.BindingContext = errorViewModel;
+			previewPage.ChangePage(errorPage);
+		}
+
+		protected virtual async Task PreviewPage(Page page)
+		{
+			await EnsurePresented();
+			NavigationPage.SetHasNavigationBar(previewPage, true);
+			previewPage.ChangePage(page);
+		}
+
+		protected virtual Page CreateViewFromResult(EvalResult res)
+		{
+			if (res.HasResult)
+			{
+				return res.Result as Page;
+			}
 			var result = TypeActivator(res.ResultType);
 			Page page = result as Page;
 			if (page == null && result is View view)
@ -56,18 +84,8 @@ namespace XAMLator.Server
 				{
 					page.BindingContext = viewModel;
 				}
-				await EnsurePresented();
-				NavigationPage.SetHasNavigationBar(previewPage, true);
-				previewPage.ChangePage(page);
 			}
-		}
-
-		public virtual async Task NotifyError(ErrorViewModel errorViewModel)
-		{
-			await EnsurePresented();
-			errorViewModel.CloseCommand = closeCommand;
-			errorPage.BindingContext = errorViewModel;
-			previewPage.ChangePage(errorPage);
+			return page;
 		}

 		protected virtual Task ShowPreviewPage(Page previewPage)
--- a/XAMLator.Server.Shared/UIToolkit.cs
+++ b/XAMLator.Server.Shared/UIToolkit.cs
@ -0,0 +1,31 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator.Server
+{
+	public class UIToolkit : IUIToolkit
+	{
+		public void RunInUIThread(Action action)
+		{
+			Xamarin.Forms.Device.BeginInvokeOnMainThread(action);
+		}
+
+		public Task RunInUIThreadAsync(Func<Task> action)
+		{
+			var tcs = new TaskCompletionSource<bool>();
+			Action asyncAction = () =>
+			{
+				try
+				{
+					action().ContinueWith((r) => tcs.SetResult(true));
+				}
+				catch (Exception ex)
+				{
+					tcs.SetException(ex);
+				}
+			};
+			Xamarin.Forms.Device.BeginInvokeOnMainThread(asyncAction);
+			return tcs.Task;
+		}
+	}
+}
--- a/XAMLator.Server.Shared/VM.cs
+++ b/XAMLator.Server.Shared/VM.cs
@ -13,7 +13,7 @@ namespace XAMLator.Server
 	public class VM
 	{
 		static MethodInfo loadXAML;
-		static EvalRequest currentEvalRequest;
+		static EvalRequestMessage currentEvalRequest;
 		readonly object mutex = new object();
 		IEvaluator evaluator;

@ -38,7 +38,7 @@ namespace XAMLator.Server
 			loadXAML.Invoke(null, new object[] { view, currentEvalRequest.Xaml });
 		}

-		public Task<EvalResult> Eval(EvalRequest code, TaskScheduler mainScheduler, CancellationToken token)
+		public Task<EvalResult> Eval(EvalRequestMessage code, TaskScheduler mainScheduler, CancellationToken token)
 		{
 			var tcs = new TaskCompletionSource<EvalResult>();
 			var r = new EvalResult();
@ -60,7 +60,7 @@ namespace XAMLator.Server
 			}
 		}

-		async Task<EvalResult> EvalOnMainThread(EvalRequest code, CancellationToken token)
+		async Task<EvalResult> EvalOnMainThread(EvalRequestMessage code, CancellationToken token)
 		{
 			EvalResult evalResult = new EvalResult();

@ -71,15 +71,17 @@ namespace XAMLator.Server
 			sw.Start();

 			currentEvalRequest = code;
-			object newType;
-
 			if (evaluator.IsEvaluationSupported)
 			{
 				if (code.NeedsRebuild)
 				{
-					await evaluator.EvaluateCode(code.Declarations, evalResult);
+					await evaluator.EvaluateCode($"new {code.NewTypeName} ()", evalResult, code.Declarations);
+					if (!evalResult.HasErrors && evalResult.HasResult)
+					{
+						evalResult.ResultType = evalResult.Result.GetType();
+					}
 				}
-				if (!evalResult.HasErrors)
+				else
 				{
 					evalResult.ResultType = GetTypeByName(code.NewTypeName);
 				}
@ -135,6 +137,10 @@ namespace XAMLator.Server
 		static string LoadResource(AssemblyName assemblyName, string name)
 		{
 			Log.Information($"Resolving resource {name}");
+			if (currentEvalRequest == null)
+			{
+				return null;
+			}
 			if (name == currentEvalRequest.XamlResourceName)
 			{
 				return currentEvalRequest.Xaml;
--- a/XAMLator.Server.Shared/XAMLator.Server.Shared.projitems
+++ b/XAMLator.Server.Shared/XAMLator.Server.Shared.projitems
@ -19,6 +19,8 @@
    <Compile Include="$(MSBuildThisFileDirectory)ErrorPage.xaml.cs">
      <DependentUpon>ErrorPage.xaml</DependentUpon>
    </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)AssemblyInfo.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)UIToolkit.cs" />
  </ItemGroup>
  <ItemGroup>
    <EmbeddedResource Include="$(MSBuildThisFileDirectory)ErrorPage.xaml">
--- a/XAMLator.Server.Tests/CSSUpdateFeature.cs
+++ b/XAMLator.Server.Tests/CSSUpdateFeature.cs
@ -0,0 +1,16 @@
+using System;
+using NUnit.Framework;
+
+namespace XAMLator.Server.Tests
+{
+	[TestFixture]
+	public class CSSUpdateFeature : XAMLatorFeatureBase
+	{
+
+		[Test]
+		public void When_the_css_is_updated_previewing_a_view_uses_the_new_version()
+		{
+
+		}
+	}
+}
--- a/XAMLator.Server.Tests/NonFormsTypesPreviewFeature.cs
+++ b/XAMLator.Server.Tests/NonFormsTypesPreviewFeature.cs
@ -0,0 +1,10 @@
+using System;
+namespace XAMLator.Server.Tests
+{
+	public class NonFormsTypesPreviewFeature
+	{
+		public NonFormsTypesPreviewFeature()
+		{
+		}
+	}
+}
--- a/XAMLator.Server.Tests/OpenTK.dll.config
+++ b/XAMLator.Server.Tests/OpenTK.dll.config
@ -0,0 +1,25 @@
+<configuration>
+  <dllmap os="linux" dll="opengl32.dll" target="libGL.so.1"/>
+  <dllmap os="linux" dll="glu32.dll" target="libGLU.so.1"/>
+  <dllmap os="linux" dll="openal32.dll" target="libopenal.so.1"/>
+  <dllmap os="linux" dll="alut.dll" target="libalut.so.0"/>
+  <dllmap os="linux" dll="opencl.dll" target="libOpenCL.so"/>
+  <dllmap os="linux" dll="libX11" target="libX11.so.6"/>
+  <dllmap os="linux" dll="libXi" target="libXi.so.6"/>
+  <dllmap os="linux" dll="SDL2.dll" target="libSDL2-2.0.so.0"/>
+  <dllmap os="osx" dll="opengl32.dll" target="/System/Library/Frameworks/OpenGL.framework/OpenGL"/>
+  <dllmap os="osx" dll="openal32.dll" target="/System/Library/Frameworks/OpenAL.framework/OpenAL" />
+  <dllmap os="osx" dll="alut.dll" target="/System/Library/Frameworks/OpenAL.framework/OpenAL" />
+  <dllmap os="osx" dll="libGLES.dll" target="/System/Library/Frameworks/OpenGLES.framework/OpenGLES" />
+  <dllmap os="osx" dll="libGLESv1_CM.dll" target="/System/Library/Frameworks/OpenGLES.framework/OpenGLES" />
+  <dllmap os="osx" dll="libGLESv2.dll" target="/System/Library/Frameworks/OpenGLES.framework/OpenGLES" />
+  <dllmap os="osx" dll="opencl.dll" target="/System/Library/Frameworks/OpenCL.framework/OpenCL"/>
+  <dllmap os="osx" dll="SDL2.dll" target="libSDL2.dylib"/>
+  <!-- XQuartz compatibility (X11 on Mac) -->
+  <dllmap os="osx" dll="libGL.so.1" target="/usr/X11/lib/libGL.dylib"/>
+  <dllmap os="osx" dll="libX11" target="/usr/X11/lib/libX11.dylib"/>
+  <dllmap os="osx" dll="libXcursor.so.1" target="/usr/X11/lib/libXcursor.dylib"/>
+  <dllmap os="osx" dll="libXi" target="/usr/X11/lib/libXi.dylib"/>
+  <dllmap os="osx" dll="libXinerama" target="/usr/X11/lib/libXinerama.dylib"/>
+  <dllmap os="osx" dll="libXrandr.so.2" target="/usr/X11/lib/libXrandr.dylib"/>
+</configuration>
--- a/XAMLator.Server.Tests/SetupClass.cs
+++ b/XAMLator.Server.Tests/SetupClass.cs
@ -0,0 +1,16 @@
+using System;
+using NUnit.Framework;
+using Xamarin.Forms;
+
+namespace XAMLator.Server.Tests
+{
+	[SetUpFixture]
+	public class SetupClass
+	{
+		[OneTimeSetUp]
+		public void Setup()
+		{
+			Forms.Init();
+		}
+	}
+}
--- a/XAMLator.Server.Tests/TestPage.xaml
+++ b/XAMLator.Server.Tests/TestPage.xaml
@ -0,0 +1,6 @@
+<?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="XAMLator.Server.Tests.TestPage">
+    <ContentPage.Content>
+        <Label x:Name="label" Text="Sample"/>
+    </ContentPage.Content>
+</ContentPage>
--- a/XAMLator.Server.Tests/TestPage.xaml.cs
+++ b/XAMLator.Server.Tests/TestPage.xaml.cs
@ -0,0 +1,12 @@
+using Xamarin.Forms;
+
+namespace XAMLator.Server.Tests
+{
+	public partial class TestPage : ContentPage
+	{
+		public TestPage()
+		{
+			InitializeComponent();
+		}
+	}
+}
--- a/XAMLator.Server.Tests/TestPreviewer.cs
+++ b/XAMLator.Server.Tests/TestPreviewer.cs
@ -0,0 +1,60 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Xamarin.Forms;
+
+namespace XAMLator.Server.Tests
+{
+	public enum PreviewState
+	{
+		None,
+		Error,
+		Preview
+	}
+
+	public class TestPreviewer : Previewer
+	{
+		public TestPreviewer(Dictionary<Type, object> viewModelsMapping) : base(viewModelsMapping) { }
+
+		public PreviewState State { get; private set; }
+
+		public ErrorViewModel ErrorViewModel { get; private set; }
+
+		public EvalResult EvalResult { get; private set; }
+
+		public Page PreviewedPage { get; private set; }
+
+		public override Task NotifyError(ErrorViewModel errorViewModel)
+		{
+			State = PreviewState.Error;
+			ErrorViewModel = errorViewModel;
+			EvalResult = null;
+			return base.NotifyError(errorViewModel);
+		}
+
+		public override Task Preview(EvalResult res)
+		{
+			State = PreviewState.Preview;
+			ErrorViewModel = null;
+			EvalResult = res;
+			return base.Preview(res);
+		}
+
+		protected override Task PreviewPage(Page page)
+		{
+			PreviewedPage = page;
+			return Task.FromResult(true);
+		}
+
+		protected override Task HidePreviewPage(Page previewPage)
+		{
+			return Task.FromResult(true);
+		}
+
+		protected override Task ShowPreviewPage(Page previewPage)
+		{
+			PreviewedPage = previewPage;
+			return Task.FromResult(true);
+		}
+	}
+}
--- a/XAMLator.Server.Tests/TestTCPCommunicator.cs
+++ b/XAMLator.Server.Tests/TestTCPCommunicator.cs
@ -0,0 +1,47 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator.Server.Tests
+{
+	public class TestTCPCommunicator : ITcpCommunicatorClient, ITcpCommunicatorServer
+	{
+		public event EventHandler<object> DataReceived;
+		public event EventHandler ClientConnected;
+
+		public int ClientsCount { get; private set; }
+
+		public Task<bool> Connect(string ip, int port)
+		{
+			ClientsCount++;
+			return Task.FromResult(true);
+		}
+
+		public void Disconnect()
+		{
+			ClientsCount--;
+		}
+
+		public Task<bool> Send<T>(T obj)
+		{
+			try
+			{
+				DataReceived?.Invoke(this, Serializer.DeserializeJson(Serializer.SerializeJson(obj)));
+				return Task.FromResult(true);
+			}
+			catch (Exception ex)
+			{
+				Log.Exception(ex);
+				return Task.FromResult(false);
+			}
+		}
+
+		public Task<bool> StartListening(int serverPort)
+		{
+			return Task.FromResult(true);
+		}
+
+		public void StopListening()
+		{
+		}
+	}
+}
--- a/XAMLator.Server.Tests/TestUIToolkit.cs
+++ b/XAMLator.Server.Tests/TestUIToolkit.cs
@ -0,0 +1,18 @@
+using System;
+using System.Threading.Tasks;
+
+namespace XAMLator.Server.Tests
+{
+	public class TestUIToolkit : IUIToolkit
+	{
+		public void RunInUIThread(Action action)
+		{
+			action();
+		}
+
+		public Task RunInUIThreadAsync(Func<Task> action)
+		{
+			return action();
+		}
+	}
+}
--- a/XAMLator.Server.Tests/TestWorkspace.cs
+++ b/XAMLator.Server.Tests/TestWorkspace.cs
@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+using NUnit.Framework;
+
+namespace XAMLator.Server.Tests
+{
+	public class TestWorkspace : IDisposable
+	{
+		AdhocWorkspace workspace;
+
+		public TestWorkspace(string tempDir)
+		{
+			CopyFile(TestProjectDir, "TestPage.xaml", tempDir);
+			CopyFile(TestProjectDir, "TestPage.xaml.cs", tempDir);
+			CopyFile(TestAutogenDir, "TestPage.xaml.g.cs", tempDir);
+			workspace = new AdhocWorkspace();
+			var solution = SolutionInfo.Create(SolutionId.CreateNewId(), VersionStamp.Default);
+			workspace.AddSolution(solution);
+			var projectId = ProjectId.CreateNewId();
+			var versionStamp = VersionStamp.Create();
+			var projectInfo = ProjectInfo.Create(projectId, versionStamp, "TestProject", "TestProject", LanguageNames.CSharp);
+			var testProject = workspace.AddProject(projectInfo);
+			AddReferences(testProject);
+			AddDocument(testProject, tempDir, "TestPage.xaml.cs");
+			AddDocument(testProject, tempDir, "TestPage.xaml");
+			AddDocument(testProject, tempDir, "TestPage.xaml.g.cs");
+		}
+
+		public void Dispose()
+		{
+			workspace.Dispose();
+		}
+
+		public Document TestPageDoc => FindDocument("TestPage.xaml.cs");
+
+		string TestProjectDir => Path.Combine(TestContext.CurrentContext.TestDirectory, "..", "..");
+
+		string TestAutogenDir => Path.Combine(TestProjectDir, "obj", "Debug");
+
+		public Document FindDocument(string docName)
+		{
+			return workspace.CurrentSolution.Projects.Single().Documents.Single(d => d.Name == docName);
+		}
+
+		public void UpdateDocument(ref Document document, string code)
+		{
+			var newSolution = workspace.CurrentSolution.WithDocumentText(
+				document.Id, SourceText.From(code), PreservationMode.PreserveIdentity);
+			workspace.TryApplyChanges(newSolution);
+			document = workspace.CurrentSolution.GetDocument(document.Id);
+		}
+
+		void CopyFile(string dir, string fileName, string outDir)
+		{
+			File.Copy(Path.Combine(dir, fileName), Path.Combine(outDir, fileName), true);
+		}
+
+		Document AddDocument(Project testProject, string dir, string fileName)
+		{
+			DocumentInfo documentInfo = DocumentInfo.Create(
+				DocumentId.CreateNewId(testProject.Id),
+				fileName,
+				new List<string> { dir },
+				SourceCodeKind.Regular,
+				TextLoader.From(TextAndVersion.Create(ReadFile(dir, fileName), VersionStamp.Create())),
+				Path.Combine(dir, fileName));
+			return workspace.AddDocument(documentInfo);
+		}
+
+		SourceText ReadFile(string dir, string fileName)
+		{
+			return SourceText.From(File.ReadAllText(Path.Combine(dir, fileName)));
+		}
+
+		void AddReferences(Project project)
+		{
+			foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
+			{
+				if (!assembly.IsDynamic)
+				{
+					project.AddMetadataReference(MetadataReference.CreateFromFile(assembly.Location));
+				}
+			}
+		}
+	}
+}
--- a/XAMLator.Server.Tests/UsageFeature.cs
+++ b/XAMLator.Server.Tests/UsageFeature.cs
@ -0,0 +1,29 @@
+using System;
+using System.Threading.Tasks;
+using NUnit.Framework;
+
+namespace XAMLator.Server.Tests
+{
+	[TestFixture]
+	public class UsageFeature : XAMLatorFeatureBase
+	{
+		[Test]
+		public async Task A_xaml_changes_after_a_code_behind_and_the_view_is_previewed()
+		{
+			await When_a_csharp_document_changes("TestPage.xaml.cs");
+			When_a_xaml_document_changes("TestPage.xaml");
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("XAMLator.Server.Tests.TestPage1", previewer.EvalResult.ResultType.FullName);
+		}
+
+		[Test]
+		public async Task A_code_behind_changes_after_xaml_and_the_view_is_previewed()
+		{
+			When_a_xaml_document_changes("TestPage.xaml");
+			await When_a_csharp_document_changes("TestPage.xaml.cs");
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("XAMLator.Server.Tests.TestPage1", previewer.EvalResult.ResultType.FullName);
+		}
+
+	}
+}
--- a/XAMLator.Server.Tests/ViewWithoutXAMLPreviewFeature.cs
+++ b/XAMLator.Server.Tests/ViewWithoutXAMLPreviewFeature.cs
@ -0,0 +1,10 @@
+using System;
+namespace XAMLator.Server.Tests
+{
+	public class ViewWithoutXAMLPreviewFeature
+	{
+		public ViewWithoutXAMLPreviewFeature()
+		{
+		}
+	}
+}
--- a/XAMLator.Server.Tests/XAMLAndCodeBehindPreviewFeature.cs
+++ b/XAMLator.Server.Tests/XAMLAndCodeBehindPreviewFeature.cs
@ -0,0 +1,56 @@
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Xamarin.Forms;
+
+namespace XAMLator.Server.Tests
+{
+	[TestFixture]
+	public class XAMLAndCodeBehindPreviewFeature : XAMLatorFeatureBase
+	{
+		[Test]
+		public async Task A_code_behind_changes_the_first_time_and_the_view_is_previewed_with_a_new_type()
+		{
+			await When_a_csharp_document_changes("TestPage.xaml.cs");
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("XAMLator.Server.Tests.TestPage1", previewer.EvalResult.ResultType.FullName);
+		}
+
+		[Test]
+		public async Task When_the_code_changes_the_text_of_a_label_the_view_is_updated()
+		{
+			await When_the_code_changes("TestPage.xaml.cs", @"
+			    using Xamarin.Forms;
+                namespace XAMLator.Server.Tests{
+                    public partial class TestPage : ContentPage {
+	              	    public TestPage() {
+			                InitializeComponent();
+                            label.Text = ""NEW TEXT"";
+	                    }}}");
+			var label = (previewer.PreviewedPage as ContentPage).Content as Label;
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("NEW TEXT", label.Text);
+		}
+
+		[Test]
+		public async Task When_the_code_contains_errors_the_error_page_is_shown()
+		{
+			await When_the_code_changes("TestPage.xaml.cs", @"
+			    using Xamarin.Forms;
+                namespace XAMLator.Server.Tests{
+                    public partial class TestPage : ContentPage {
+	              	    public TestPage() {
+			                InvalidMethod();
+	                    }}}");
+			Assert.AreEqual(PreviewState.Error, previewer.State);
+			Assert.AreEqual("Oh no! An evaluation error!", previewer.ErrorViewModel.Title);
+		}
+
+		[Test]
+		public async Task When_the_code_is_not_parsable_the_error_page_is_shown()
+		{
+			await When_the_code_changes("TestPage.xaml.cs", @"public new {}");
+			Assert.AreEqual(PreviewState.Error, previewer.State);
+			Assert.AreEqual("Oh no! An exception!", previewer.ErrorViewModel.Title);
+		}
+	}
+}
--- a/XAMLator.Server.Tests/XAMLEvaluationFeature.cs
+++ b/XAMLator.Server.Tests/XAMLEvaluationFeature.cs
@ -0,0 +1,82 @@
+using NUnit.Framework;
+using Xamarin.Forms;
+
+namespace XAMLator.Server.Tests
+{
+	[TestFixture]
+	public class XAMLEvaluationFeature : XAMLatorFeatureBase
+	{
+
+		[Test]
+		public void A_xaml_changes_and_the_view_is_previewed()
+		{
+			When_a_xaml_document_changes("TestPage.xaml");
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("XAMLator.Server.Tests.TestPage", previewer.EvalResult.ResultType.FullName);
+		}
+
+		[Test]
+		public void When_a_xaml_element_name_is_changed_the_code_behind_is_autogenerated()
+		{
+			When_a_xaml_document_changes("TestPage.xaml",
+				@"<?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=""XAMLator.Server.Tests.TestPage"">
+    					<ContentPage.Content>
+        					<Label x:Name=""newLabel"" Text=""Sample""/>
+    					</ContentPage.Content>
+				</ContentPage>
+			".Trim());
+
+			var contentPage = previewer.PreviewedPage as ContentPage;
+
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("Sample", contentPage.FindByName<Label>("newLabel").Text);
+		}
+
+		[Test]
+		public void When_a_xaml_changes_the_previwed_view_has_the_new_changes()
+		{
+			When_a_xaml_document_changes("TestPage.xaml",
+				@"<?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=""XAMLator.Server.Tests.TestPage"">
+    					<ContentPage.Content>
+        					<Label x:Name=""newLabel"" Text=""New text""/>
+    					</ContentPage.Content>
+				</ContentPage>
+			".Trim());
+			var contentPage = previewer.PreviewedPage as ContentPage;
+
+			Assert.AreEqual(PreviewState.Preview, previewer.State);
+			Assert.AreEqual("New text", (contentPage.Content as Label).Text);
+		}
+
+		[Test]
+		public void When_the_xaml_contains_a_sytax_error_the_error_page_is_shown()
+		{
+			When_a_xaml_document_changes("TestPage.xaml", @"
+				<?xml version=""1.0"" encoding=""UTF-8""?>
+				<ContentPage".Trim());
+			Assert.AreEqual(PreviewState.Error, previewer.State);
+		}
+
+		[Test]
+		public void When_the_xaml_contains_an_error_the_error_page_is_shown()
+		{
+			When_a_xaml_document_changes("TestPage.xaml",
+				@"<?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=""XAMLator.Server.Tests.TestPage"">
+    					<ContentPage.Cotent>
+        					<Label x:Name=""newLabel"" Text=""Sample""/>
+    					</ContentPage.Cotent>
+				</ContentPage>
+			".Trim());
+			Assert.AreEqual(PreviewState.Error, previewer.State);
+		}
+	}
+}
--- a/XAMLator.Server.Tests/XAMLator.Server.Tests.csproj
+++ b/XAMLator.Server.Tests/XAMLator.Server.Tests.csproj
@ -0,0 +1,236 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\XAMLator.Client\XAMLator.Client.projitems" Label="Shared" Condition="Exists('..\XAMLator.Client\XAMLator.Client.projitems')" />
+  <Import Project="..\packages\Xamarin.Forms.3.4.0.1008975\build\Xamarin.Forms.props" Condition="Exists('..\packages\Xamarin.Forms.3.4.0.1008975\build\Xamarin.Forms.props')" />
+  <Import Project="..\packages\NUnit.3.11.0\build\NUnit.props" Condition="Exists('..\packages\NUnit.3.11.0\build\NUnit.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <RootNamespace>XAMLator.Server.Tests</RootNamespace>
+    <AssemblyName>XAMLator.Server.Tests</AssemblyName>
+    <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
+    <XFDisableFrameworkVersionValidation>True</XFDisableFrameworkVersionValidation>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug</OutputPath>
+    <DefineConstants>DEBUG;</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release</OutputPath>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="nunit.framework">
+      <HintPath>..\packages\NUnit.3.11.0\lib\net45\nunit.framework.dll</HintPath>
+    </Reference>
+    <Reference Include="SQLitePCLRaw.core">
+      <HintPath>..\packages\SQLitePCLRaw.core.1.1.2\lib\net45\SQLitePCLRaw.core.dll</HintPath>
+    </Reference>
+    <Reference Include="SQLitePCLRaw.provider.e_sqlite3">
+      <HintPath>..\packages\SQLitePCLRaw.provider.e_sqlite3.net45.1.1.2\lib\net45\SQLitePCLRaw.provider.e_sqlite3.dll</HintPath>
+    </Reference>
+    <Reference Include="SQLitePCLRaw.batteries_green">
+      <HintPath>..\packages\SQLitePCLRaw.bundle_green.1.1.2\lib\net45\SQLitePCLRaw.batteries_green.dll</HintPath>
+    </Reference>
+    <Reference Include="SQLitePCLRaw.batteries_v2">
+      <HintPath>..\packages\SQLitePCLRaw.bundle_green.1.1.2\lib\net45\SQLitePCLRaw.batteries_v2.dll</HintPath>
+    </Reference>
+    <Reference Include="System.AppContext">
+      <HintPath>..\packages\System.AppContext.4.3.0\lib\net46\System.AppContext.dll</HintPath>
+    </Reference>
+    <Reference Include="mscorlib" />
+    <Reference Include="System.Core" />
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+    </Reference>
+    <Reference Include="System.Composition.AttributedModel">
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+    <Reference Include="System.Composition.Convention">
+      <HintPath>..\packages\System.Composition.Convention.1.0.31\lib\portable-net45+win8+wp8+wpa81\System.Composition.Convention.dll</HintPath>
+    </Reference>
+    <Reference Include="System.Composition.Runtime">
+      <HintPath>..\packages\System.Composition.Runtime.1.0.31\lib\portable-net45+win8+wp8+wpa81\System.Composition.Runtime.dll</HintPath>
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+      <HintPath>..\packages\System.Composition.Hosting.1.0.31\lib\portable-net45+win8+wp8+wpa81\System.Composition.Hosting.dll</HintPath>
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+    </Reference>
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+    </Reference>
+    <Reference Include="Microsoft.CodeAnalysis.Workspaces">
+      <HintPath>..\packages\Microsoft.CodeAnalysis.Workspaces.Common.2.10.0\lib\net46\Microsoft.CodeAnalysis.Workspaces.dll</HintPath>
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+      <HintPath>..\packages\Microsoft.CodeAnalysis.Workspaces.MSBuild.2.10.0\lib\net46\Microsoft.CodeAnalysis.Workspaces.MSBuild.dll</HintPath>
+    </Reference>
+    <Reference Include="Xamarin.Forms.Core">
+      <HintPath>..\packages\Xamarin.Forms.3.4.0.1008975\lib\netstandard2.0\Xamarin.Forms.Core.dll</HintPath>
+    </Reference>
+    <Reference Include="Xamarin.Forms.Platform">
+      <HintPath>..\packages\Xamarin.Forms.3.4.0.1008975\lib\netstandard2.0\Xamarin.Forms.Platform.dll</HintPath>
+    </Reference>
+    <Reference Include="Xamarin.Forms.Xaml">
+      <HintPath>..\packages\Xamarin.Forms.3.4.0.1008975\lib\netstandard2.0\Xamarin.Forms.Xaml.dll</HintPath>
+    </Reference>
+    <Reference Include="OpenTK">
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+    </Reference>
+    <Reference Include="webkit-sharp">
+      <HintPath>..\packages\Xamarin.Forms.Platform.GTK.3.4.0.1008975\lib\net45\webkit-sharp.dll</HintPath>
+    </Reference>
+    <Reference Include="Xamarin.Forms.Platform.GTK">
+      <HintPath>..\packages\Xamarin.Forms.Platform.GTK.3.4.0.1008975\lib\net45\Xamarin.Forms.Platform.GTK.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.CodeAnalysis.CSharp">
+      <HintPath>..\packages\Microsoft.CodeAnalysis.CSharp.2.10.0\lib\netstandard1.3\Microsoft.CodeAnalysis.CSharp.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.CodeAnalysis.CSharp.Workspaces">
+      <HintPath>..\packages\Microsoft.CodeAnalysis.CSharp.Workspaces.2.10.0\lib\netstandard1.3\Microsoft.CodeAnalysis.CSharp.Workspaces.dll</HintPath>
+    </Reference>
+    <Reference Include="Castle.Core">
+      <HintPath>..\packages\Castle.Core.4.3.1\lib\net45\Castle.Core.dll</HintPath>
+    </Reference>
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+      <HintPath>..\packages\System.Runtime.CompilerServices.Unsafe.4.5.0\lib\netstandard2.0\System.Runtime.CompilerServices.Unsafe.dll</HintPath>
+    </Reference>
+    <Reference Include="System.Threading.Tasks.Extensions">
+      <HintPath>..\packages\System.Threading.Tasks.Extensions.4.5.1\lib\netstandard2.0\System.Threading.Tasks.Extensions.dll</HintPath>
+    </Reference>
+    <Reference Include="Moq">
+      <HintPath>..\packages\Moq.4.10.1\lib\net45\Moq.dll</HintPath>
+    </Reference>
+    <Reference Include="Xamarin.Forms.Build.Tasks">
+      <HintPath>..\packages\Xamarin.Forms.3.2.0.839982\build\netstandard2.0\Xamarin.Forms.Build.Tasks.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.Build.Framework">
+      <HintPath>..\packages\Microsoft.Build.Framework.15.9.20\lib\net46\Microsoft.Build.Framework.dll</HintPath>
+    </Reference>
+    <Reference Include="System.Xaml" />
+    <Reference Include="Microsoft.VisualStudio.Setup.Configuration.Interop">
+      <HintPath>..\packages\Microsoft.VisualStudio.Setup.Configuration.Interop.1.16.30\lib\net35\Microsoft.VisualStudio.Setup.Configuration.Interop.dll</HintPath>
+    </Reference>
+    <Reference Include="System.Runtime.InteropServices.RuntimeInformation">
+      <HintPath>..\packages\System.Runtime.InteropServices.RuntimeInformation.4.3.0\lib\net45\System.Runtime.InteropServices.RuntimeInformation.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.Build.Utilities.Core">
+      <HintPath>..\packages\Microsoft.Build.Utilities.Core.15.9.20\lib\net46\Microsoft.Build.Utilities.Core.dll</HintPath>
+    </Reference>
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="XAMLEvaluationFeature.cs" />
+    <Compile Include="TestPage.xaml.cs">
+      <DependentUpon>TestPage.xaml</DependentUpon>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Compile>
+    <Compile Include="TestWorkspace.cs" />
+    <Compile Include="SetupClass.cs" />
+    <Compile Include="TestTCPCommunicator.cs" />
+    <Compile Include="TestUIToolkit.cs" />
+    <Compile Include="XAMLAndCodeBehindPreviewFeature.cs" />
+    <Compile Include="ViewWithoutXAMLPreviewFeature.cs" />
+    <Compile Include="NonFormsTypesPreviewFeature.cs" />
+    <Compile Include="TestPreviewer.cs" />
+    <Compile Include="XAMLatorFeatureBase.cs" />
+    <Compile Include="UsageFeature.cs" />
+    <Compile Include="CSSUpdateFeature.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="TestPage.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </EmbeddedResource>
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\XAMLator.Server.Net461\XAMLator.Server.Mono.Net461.csproj">
+      <Project>{E3F80ADC-71F8-454E-BA3B-87BD0D78B051}</Project>
+      <Name>XAMLator.Server.Mono.Net461</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+    <None Include="webkit-sharp.dll.config" />
+    <None Include="OpenTK.dll.config" />
+  </ItemGroup>
+  <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
+  <Import Project="..\packages\SQLitePCLRaw.lib.e_sqlite3.linux.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.linux.targets" Condition="Exists('..\packages\SQLitePCLRaw.lib.e_sqlite3.linux.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.linux.targets')" />
+  <Import Project="..\packages\SQLitePCLRaw.lib.e_sqlite3.osx.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.osx.targets" Condition="Exists('..\packages\SQLitePCLRaw.lib.e_sqlite3.osx.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.osx.targets')" />
+  <Import Project="..\packages\SQLitePCLRaw.lib.e_sqlite3.v110_xp.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.v110_xp.targets" Condition="Exists('..\packages\SQLitePCLRaw.lib.e_sqlite3.v110_xp.1.1.2\build\SQLitePCLRaw.lib.e_sqlite3.v110_xp.targets')" />
+  <Import Project="..\packages\Xamarin.Forms.3.4.0.1008975\build\Xamarin.Forms.targets" Condition="Exists('..\packages\Xamarin.Forms.3.4.0.1008975\build\Xamarin.Forms.targets')" />
+</Project>
--- a/XAMLator.Server.Tests/XAMLatorFeatureBase.cs
+++ b/XAMLator.Server.Tests/XAMLatorFeatureBase.cs
@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Moq;
+using NUnit.Framework;
+using XAMLator.Client;
+
+namespace XAMLator.Server.Tests
+{
+	public class XAMLatorFeatureBase
+	{
+		protected TestPreviewer previewer;
+		protected TestWorkspace workspace;
+		protected Mock<IIDE> ideMock;
+		protected TestTCPCommunicator tcpCommunicator;
+		protected TestUIToolkit uiToolkit;
+		protected XAMLatorMonitor xamlatorMonitor;
+		protected PreviewServer previewServer;
+		string tempDir;
+
+		[SetUp]
+		public async Task Given_a_xamlator_server_listening()
+		{
+			SynchronizationContext.SetSynchronizationContext(new SynchronizationContext());
+			tempDir = GetTemporaryDirectory();
+			workspace = new TestWorkspace(tempDir);
+			ideMock = new Mock<IIDE>();
+			tcpCommunicator = new TestTCPCommunicator();
+			uiToolkit = new TestUIToolkit();
+
+			xamlatorMonitor = new XAMLatorMonitor(ideMock.Object, tcpCommunicator);
+
+			previewer = new TestPreviewer(new Dictionary<Type, object>());
+			previewServer = new PreviewServer();
+			await previewServer.RunInternal(null, previewer, null, Constants.DEFAULT_PORT, uiToolkit, tcpCommunicator);
+		}
+
+		[TearDown]
+		public void TearDown()
+		{
+			FormsViewClassDeclaration.Reset();
+			Directory.Delete(tempDir, true);
+		}
+
+		protected async Task When_a_csharp_document_changes(string docName)
+		{
+			var doc = workspace.FindDocument(docName);
+
+			EmitDocumentChanged(doc.FilePath, "",
+				await doc.GetSyntaxTreeAsync(), await doc.GetSemanticModelAsync());
+		}
+
+		protected async Task When_the_code_changes(string docName, string code)
+		{
+			Document doc = workspace.FindDocument(docName);
+			workspace.UpdateDocument(ref doc, code);
+			EmitDocumentChanged(doc.FilePath, code,
+				await doc.GetSyntaxTreeAsync(), await doc.GetSemanticModelAsync());
+		}
+
+		protected void When_a_xaml_document_changes(string docName)
+		{
+			var doc = workspace.FindDocument(docName);
+			EmitDocumentChanged(doc.FilePath, File.ReadAllText(doc.FilePath));
+		}
+
+		protected void When_a_xaml_document_changes(string docName, string xaml)
+		{
+			var doc = workspace.FindDocument(docName);
+			EmitDocumentChanged(doc.FilePath, xaml);
+		}
+
+		protected void EmitDocumentChanged(string filePath, string content,
+			SyntaxTree syntaxTree = null, SemanticModel semanticModel = null)
+		{
+			var args = new DocumentChangedEventArgs(filePath, content, syntaxTree, semanticModel);
+			ideMock.Raise((IIDE obj) => obj.DocumentChanged += null, this, args);
+		}
+
+		string GetTemporaryDirectory()
+		{
+			string tempDirectory = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
+			Directory.CreateDirectory(tempDirectory);
+			return tempDirectory;
+		}
+	}
+}
--- a/XAMLator.Server.Tests/packages.config
+++ b/XAMLator.Server.Tests/packages.config
@ -0,0 +1,72 @@
+<?xml version="1.0" encoding="utf-8"?>
+<packages>
+  <package id="Castle.Core" version="4.3.1" targetFramework="net461" />
+  <package id="Microsoft.Build.Framework" version="15.9.20" targetFramework="net461" />
+  <package id="Microsoft.Build.Utilities.Core" version="15.9.20" targetFramework="net461" />
+  <package id="Microsoft.CodeAnalysis.Analyzers" version="2.6.1" targetFramework="net461" developmentDependency="true" />
+  <package id="Microsoft.CodeAnalysis.Common" version="2.10.0" targetFramework="net461" />
+  <package id="Microsoft.CodeAnalysis.CSharp" version="2.10.0" targetFramework="net461" />
+  <package id="Microsoft.CodeAnalysis.CSharp.Workspaces" version="2.10.0" targetFramework="net461" />
+  <package id="Microsoft.CodeAnalysis.Workspaces.Common" version="2.10.0" targetFramework="net461" />
+  <package id="Microsoft.CodeAnalysis.Workspaces.MSBuild" version="2.10.0" targetFramework="net461" />
+  <package id="Microsoft.VisualStudio.Setup.Configuration.Interop" version="1.16.30" targetFramework="net461" developmentDependency="true" />
+  <package id="Moq" version="4.10.1" targetFramework="net461" />
+  <package id="NUnit" version="3.11.0" targetFramework="net461" />
+  <package id="SQLitePCLRaw.bundle_green" version="1.1.2" targetFramework="net461" />
+  <package id="SQLitePCLRaw.core" version="1.1.2" targetFramework="net461" />
+  <package id="SQLitePCLRaw.lib.e_sqlite3.linux" version="1.1.2" targetFramework="net461" />
+  <package id="SQLitePCLRaw.lib.e_sqlite3.osx" version="1.1.2" targetFramework="net461" />
+  <package id="SQLitePCLRaw.lib.e_sqlite3.v110_xp" version="1.1.2" targetFramework="net461" />
+  <package id="SQLitePCLRaw.provider.e_sqlite3.net45" version="1.1.2" targetFramework="net461" />
+  <package id="System.AppContext" version="4.3.0" targetFramework="net461" />
+  <package id="System.Collections" version="4.3.0" targetFramework="net461" />
+  <package id="System.Collections.Concurrent" version="4.3.0" targetFramework="net461" />
+  <package id="System.Collections.Immutable" version="1.5.0" targetFramework="net461" />
+  <package id="System.Composition" version="1.0.31" targetFramework="net461" />
+  <package id="System.Composition.AttributedModel" version="1.0.31" targetFramework="net461" />
+  <package id="System.Composition.Convention" version="1.0.31" targetFramework="net461" />
+  <package id="System.Composition.Hosting" version="1.0.31" targetFramework="net461" />
+  <package id="System.Composition.Runtime" version="1.0.31" targetFramework="net461" />
+  <package id="System.Composition.TypedParts" version="1.0.31" targetFramework="net461" />
+  <package id="System.Console" version="4.3.0" targetFramework="net461" />
+  <package id="System.Diagnostics.Debug" version="4.3.0" targetFramework="net461" />
+  <package id="System.Diagnostics.FileVersionInfo" version="4.3.0" targetFramework="net461" />
+  <package id="System.Diagnostics.StackTrace" version="4.3.0" targetFramework="net461" />
+  <package id="System.Diagnostics.Tools" version="4.3.0" targetFramework="net461" />
+  <package id="System.Dynamic.Runtime" version="4.3.0" targetFramework="net461" />
+  <package id="System.Globalization" version="4.3.0" targetFramework="net461" />
+  <package id="System.IO.Compression" version="4.3.0" targetFramework="net461" />
+  <package id="System.IO.FileSystem" version="4.3.0" targetFramework="net461" />
+  <package id="System.IO.FileSystem.Primitives" version="4.3.0" targetFramework="net461" />
+  <package id="System.Linq" version="4.3.0" targetFramework="net461" />
+  <package id="System.Linq.Expressions" version="4.3.0" targetFramework="net461" />
+  <package id="System.Reflection" version="4.3.0" targetFramework="net461" />
+  <package id="System.Reflection.Metadata" version="1.6.0" targetFramework="net461" />
+  <package id="System.Resources.ResourceManager" version="4.3.0" targetFramework="net461" />
+  <package id="System.Runtime" version="4.3.0" targetFramework="net461" />
+  <package id="System.Runtime.CompilerServices.Unsafe" version="4.5.0" targetFramework="net461" />
+  <package id="System.Runtime.Extensions" version="4.3.0" targetFramework="net461" />
+  <package id="System.Runtime.InteropServices" version="4.3.0" targetFramework="net461" />
+  <package id="System.Runtime.InteropServices.RuntimeInformation" version="4.3.0" targetFramework="net461" />
+  <package id="System.Runtime.Numerics" version="4.3.0" targetFramework="net461" />
+  <package id="System.Security.Cryptography.Algorithms" version="4.3.0" targetFramework="net461" />
+  <package id="System.Security.Cryptography.Encoding" version="4.3.0" targetFramework="net461" />
+  <package id="System.Security.Cryptography.Primitives" version="4.3.0" targetFramework="net461" />
+  <package id="System.Security.Cryptography.X509Certificates" version="4.3.0" targetFramework="net461" />
+  <package id="System.Text.Encoding" version="4.3.0" targetFramework="net461" />
+  <package id="System.Text.Encoding.CodePages" version="4.3.0" targetFramework="net461" />
+  <package id="System.Text.Encoding.Extensions" version="4.3.0" targetFramework="net461" />
+  <package id="System.Threading" version="4.3.0" targetFramework="net461" />
+  <package id="System.Threading.Tasks" version="4.3.0" targetFramework="net461" />
+  <package id="System.Threading.Tasks.Extensions" version="4.5.1" targetFramework="net461" />
+  <package id="System.Threading.Tasks.Parallel" version="4.3.0" targetFramework="net461" />
+  <package id="System.Threading.Thread" version="4.3.0" targetFramework="net461" />
+  <package id="System.ValueTuple" version="4.3.0" targetFramework="net461" />
+  <package id="System.Xml.ReaderWriter" version="4.3.0" targetFramework="net461" />
+  <package id="System.Xml.XDocument" version="4.3.0" targetFramework="net461" />
+  <package id="System.Xml.XmlDocument" version="4.3.0" targetFramework="net461" />
+  <package id="System.Xml.XPath" version="4.3.0" targetFramework="net461" />
+  <package id="System.Xml.XPath.XDocument" version="4.3.0" targetFramework="net461" />
+  <package id="Xamarin.Forms" version="3.4.0.1008975" targetFramework="net461" />
+  <package id="Xamarin.Forms.Platform.GTK" version="3.4.0.1008975" targetFramework="net461" />
+</packages>
--- a/XAMLator.Server.Tests/webkit-sharp.dll.config
+++ b/XAMLator.Server.Tests/webkit-sharp.dll.config
@ -0,0 +1,5 @@
+<configuration>
+  <dllmap dll="webkit-1.0" target="libwebkitgtk-1.0.0.dylib"/>
+  <dllmap dll="webkit-1.0" os="linux" target="libwebkitgtk-1.0.so.0"/>
+  <dllmap dll="webkit-1.0" os="windows" target="libwebkitgtk-1.0-0.dll"/>
+</configuration>
--- a/XAMLator.Server/RoslynEvaluator.cs
+++ b/XAMLator.Server/RoslynEvaluator.cs
@ -28,7 +28,7 @@ namespace XAMLator.Server

 		public bool IsEvaluationSupported => isEvaluationSupported;

-		public async Task<bool> EvaluateCode(string code, EvalResult result)
+		public async Task<bool> EvaluateCode(string code, EvalResult result, string initCode = null)
 		{
 			if (string.IsNullOrEmpty(code))
 			{
@ -38,7 +38,17 @@ namespace XAMLator.Server
 			EnsureConfigured();
 			try
 			{
-				var state = await CSharpScript.RunAsync(code);
+				ScriptState state;
+				if (initCode != null)
+				{
+					state = await CSharpScript.RunAsync(initCode);
+					await state.ContinueWithAsync(code);
+				}
+				else
+				{
+					state = await CSharpScript.RunAsync(code);
+				}
+				result.Result = state.ReturnValue;
 			}
 			catch (CompilationErrorException ex)
 			{
--- a/XAMLator.sln
+++ b/XAMLator.sln
@ -43,6 +43,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Tests", "Tests", "{8B24F47B
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "XAMLator.Server.Mono.Mac", "XAMLator.Server.Mac\XAMLator.Server.Mono.Mac.csproj", "{47C93CC1-2606-4130-922A-A1B2895E895E}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "XAMLator.Server.Tests", "XAMLator.Server.Tests\XAMLator.Server.Tests.csproj", "{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@ -247,6 +249,22 @@ Global
 		{47C93CC1-2606-4130-922A-A1B2895E895E}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
 		{47C93CC1-2606-4130-922A-A1B2895E895E}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
 		{47C93CC1-2606-4130-922A-A1B2895E895E}.AppStore|iPhone.Build.0 = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|Any CPU.Build.0 = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|iPhone.ActiveCfg = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Debug|iPhone.Build.0 = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|iPhone.ActiveCfg = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Release|iPhone.Build.0 = Release|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Ad-Hoc|iPhone.ActiveCfg = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF}.AppStore|iPhone.Build.0 = Debug|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{188F8020-6474-43BA-A6E7-0947C385B54C} = {72DE5BCD-BB42-41E2-916A-EEA0B7569529}
@ -264,6 +282,7 @@ Global
 		{FA699AFA-1165-40C0-AA59-BB63DA16A1B8} = {8B24F47B-470E-4237-8E2B-0A4528598FEE}
 		{B960F8D7-25B3-46E9-A95C-E539192B5744} = {A2B90814-10AD-42D8-AF1C-3272628DE819}
 		{47C93CC1-2606-4130-922A-A1B2895E895E} = {38F4F699-609F-4894-8D3F-1BA1283DAE91}
+		{55BCF24D-7424-4C5E-AD72-BB34F217EBDF} = {8B24F47B-470E-4237-8E2B-0A4528598FEE}
 	EndGlobalSection
 	GlobalSection(MonoDevelopProperties) = preSolution
 		Policies = $0