diff --git a/ILSpy/App.xaml.cs b/ILSpy/App.xaml.cs
index 39af423cb..6004486c9 100644
--- a/ILSpy/App.xaml.cs
+++ b/ILSpy/App.xaml.cs
@@ -17,6 +17,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.ComponentModel.Composition.Hosting;
 using System.Diagnostics;
 using System.Threading;
 using System.Windows;
@@ -35,6 +36,13 @@ namespace ICSharpCode.ILSpy
 		{
 			InitializeComponent();
 			
+			var catalog = new AggregateCatalog();
+			catalog.Catalogs.Add(new AssemblyCatalog(typeof(App).Assembly));
+			catalog.Catalogs.Add(new DirectoryCatalog(".", "*.Plugin.dll"));
+			var container = new CompositionContainer(catalog);
+			
+			Languages.Initialize(container);
+			
 			if (!Debugger.IsAttached) {
 				AppDomain.CurrentDomain.UnhandledException += ShowErrorBox;
 				Dispatcher.CurrentDispatcher.UnhandledException += Dispatcher_UnhandledException;
diff --git a/ILSpy/CSharpLanguage.cs b/ILSpy/CSharpLanguage.cs
index 9966b9b12..0192c43d3 100644
--- a/ILSpy/CSharpLanguage.cs
+++ b/ILSpy/CSharpLanguage.cs
@@ -19,13 +19,13 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.ComponentModel.Composition;
 using System.IO;
 using System.Linq;
 using System.Resources;
 using System.Threading.Tasks;
 using System.Xaml;
 using System.Xml;
-
 using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.Ast;
 using ICSharpCode.Decompiler.Ast.Transforms;
@@ -37,6 +37,7 @@ namespace ICSharpCode.ILSpy
 	/// <summary>
 	/// Decompiler logic for C#.
 	/// </summary>
+	[Export(typeof(Language))]
 	public class CSharpLanguage : Language
 	{
 		string name = "C#";
diff --git a/ILSpy/GacInterop.cs b/ILSpy/GacInterop.cs
index 4a0863d3c..9ab255f59 100644
--- a/ILSpy/GacInterop.cs
+++ b/ILSpy/GacInterop.cs
@@ -28,7 +28,7 @@ namespace ICSharpCode.ILSpy
 	/// <summary>
 	/// Interop with the .NET GAC.
 	/// </summary>
-	public static class GacInterop
+	static class GacInterop
 	{
 		/// <summary>
 		/// Gets the names of all assemblies in the GAC.
diff --git a/ILSpy/GuessFileType.cs b/ILSpy/GuessFileType.cs
index b27597337..72a38f210 100644
--- a/ILSpy/GuessFileType.cs
+++ b/ILSpy/GuessFileType.cs
@@ -12,7 +12,7 @@ namespace ICSharpCode.ILSpy
 	/// <summary>
 	/// Static methods for determining the type of a file.
 	/// </summary>
-	public static class GuessFileType
+	static class GuessFileType
 	{
 		public static FileType DetectFileType(Stream stream)
 		{
@@ -120,7 +120,7 @@ namespace ICSharpCode.ILSpy
 		}
 	}
 	
-	public enum FileType
+	enum FileType
 	{
 		Binary,
 		Text,
diff --git a/ILSpy/ILSpy.csproj b/ILSpy/ILSpy.csproj
index 8b3406c3a..8ed9cd687 100644
--- a/ILSpy/ILSpy.csproj
+++ b/ILSpy/ILSpy.csproj
@@ -55,6 +55,9 @@
       <RequiredTargetFramework>3.0</RequiredTargetFramework>
     </Reference>
     <Reference Include="System" />
+    <Reference Include="System.ComponentModel.Composition">
+      <RequiredTargetFramework>4.0</RequiredTargetFramework>
+    </Reference>
     <Reference Include="System.Core">
       <RequiredTargetFramework>3.5</RequiredTargetFramework>
     </Reference>
diff --git a/ILSpy/Language.cs b/ILSpy/Language.cs
index 3bce054af..238e87e63 100644
--- a/ILSpy/Language.cs
+++ b/ILSpy/Language.cs
@@ -19,6 +19,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.ComponentModel.Composition.Hosting;
 using System.Linq;
 using ICSharpCode.Decompiler;
 using Mono.Cecil;
@@ -121,19 +122,29 @@ namespace ICSharpCode.ILSpy
 	
 	public static class Languages
 	{
+		static ReadOnlyCollection<Language> allLanguages;
+		
 		/// <summary>
 		/// A list of all languages.
 		/// </summary>
-		public static readonly ReadOnlyCollection<Language> AllLanguages = new List<Language>(
-			new Language[] {
-				new CSharpLanguage(),
-				new ILLanguage(true)
+		public static ReadOnlyCollection<Language> AllLanguages {
+			get {
+				return allLanguages;
 			}
+		}
+		
+		
+		internal static void Initialize(CompositionContainer composition)
+		{
+			List<Language> languages = new List<Language>();
+			languages.AddRange(composition.GetExportedValues<Language>());
+			languages.Add(new ILLanguage(true));
 			#if DEBUG
-			.Concat(ILAstLanguage.GetDebugLanguages())
-			.Concat(CSharpLanguage.GetDebugLanguages())
+			languages.AddRange(ILAstLanguage.GetDebugLanguages());
+			languages.AddRange(CSharpLanguage.GetDebugLanguages());
 			#endif
-		).AsReadOnly();
+			allLanguages = languages.AsReadOnly();
+		}
 		
 		/// <summary>
 		/// Gets a language using its name.
diff --git a/ILSpy/NavigationHistory.cs b/ILSpy/NavigationHistory.cs
index 521780af1..f15cfa732 100644
--- a/ILSpy/NavigationHistory.cs
+++ b/ILSpy/NavigationHistory.cs
@@ -10,7 +10,7 @@ namespace ICSharpCode.ILSpy
 	/// <summary>
 	/// Stores the navigation history.
 	/// </summary>
-	public class NavigationHistory
+	sealed class NavigationHistory
 	{
 		List<SharpTreeNode> back = new List<SharpTreeNode>();
 		List<SharpTreeNode> forward = new List<SharpTreeNode>();