diff --git a/NTypewriter.Online/NTypewriter.Online.csproj.user b/NTypewriter.Online/NTypewriter.Online.csproj.user
new file mode 100644
index 0000000..94e6971
--- /dev/null
+++ b/NTypewriter.Online/NTypewriter.Online.csproj.user
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="Current" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
+    <DebuggerFlavor>ProjectDebugger</DebuggerFlavor>
+  </PropertyGroup>
+  <PropertyGroup>
+    <ActiveDebugProfile>http</ActiveDebugProfile>
+  </PropertyGroup>
+</Project>
\ No newline at end of file
diff --git a/NTypewriter.Online/Runner.cs b/NTypewriter.Online/Runner.cs
index 28aac46..2f311d5 100644
--- a/NTypewriter.Online/Runner.cs
+++ b/NTypewriter.Online/Runner.cs
@@ -9,7 +9,9 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using NTypewriter.Online.Adapters;
+using NTypewriter.Ports;
 using NTypewriter.Runtime;
+using NTypewriter.Runtime.Scripting;
 
 namespace NTypewriter.Online
 {
@@ -58,7 +60,7 @@ public async Task<Result> RunAsync(string inputCode, string template, Cancellati
 
             try
             {
-                var cmd = new RenderTemplatesCommand(null, userCodeProvider, generatedFileReaderWriter, userIO, null, null, null, null);
+                var cmd = new RenderTemplatesCommand(null, userCodeProvider, generatedFileReaderWriter, userIO, null, null, null, null, new ExpressionCompiler(References));
                 await cmd.Execute(generatorCompilation, new[] { templateToRender });
             } 
             catch (Exception ex)
diff --git a/NTypewriter.Runtime/RenderTemplatesCommand.cs b/NTypewriter.Runtime/RenderTemplatesCommand.cs
index 52e3f29..3ad0010 100644
--- a/NTypewriter.Runtime/RenderTemplatesCommand.cs
+++ b/NTypewriter.Runtime/RenderTemplatesCommand.cs
@@ -4,10 +4,12 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using NTypewriter.Editor.Config;
+using NTypewriter.Ports;
 using NTypewriter.Runtime.CodeModel;
 using NTypewriter.Runtime.CodeModel.Internals;
 using NTypewriter.Runtime.Internals;
 using NTypewriter.Runtime.Rendering;
+using NTypewriter.Runtime.Scripting;
 using NTypewriter.Runtime.UserCode;
 
 namespace NTypewriter.Runtime
@@ -36,7 +38,8 @@ public class RenderTemplatesCommand
         private readonly IUserCodeProvider userCodeProvider;
         private readonly IUserInterfaceErrorListUpdater uiErrorList; 
         private readonly IUserInterfaceOutputWriter uiOutput;        
-        private readonly IUserInterfaceStatusUpdater uiStatus;        
+        private readonly IUserInterfaceStatusUpdater uiStatus;
+        private readonly IExpressionCompiler expressionCompiler;
 
 
         public RenderTemplatesCommand(ITemplateContentLoader templateContentLoader, 
@@ -46,7 +49,9 @@ public RenderTemplatesCommand(ITemplateContentLoader templateContentLoader,
                                       ISolutionItemsManager solutionItemsManager = null,
                                       ISourceControl sourceControl = null,
                                       IUserInterfaceErrorListUpdater uiErrorList = null,
-                                      IUserInterfaceStatusUpdater uiStatus = null)
+                                      IUserInterfaceStatusUpdater uiStatus = null,
+                                      IExpressionCompiler expressionCompiler = null
+                                      )
         {
             this.templateContentLoader = templateContentLoader;
             this.userCodeProvider = userCodeProvider;
@@ -56,6 +61,7 @@ public RenderTemplatesCommand(ITemplateContentLoader templateContentLoader,
             this.solutionItemsManager = solutionItemsManager;
             this.sourceControl = sourceControl ?? NullObject.Singleton;
             this.uiStatus = uiStatus ?? NullObject.Singleton;
+            this.expressionCompiler = expressionCompiler ?? ExpressionCompiler.Default;
         }
 
 
@@ -93,7 +99,7 @@ private async Task Execute(SolutionOrCompilation roslynInput, IList<TemplateToRe
                     uiOutput.Info($"Loading template : {template.FilePath}");
                     var templateContent = template.Content ?? await templateContentLoader.Read(template.FilePath).ConfigureAwait(false);
 
-                    var templateRenderer = new TemplateRenderer(uiErrorList, uiOutput);
+                    var templateRenderer = new TemplateRenderer(uiErrorList, uiOutput, expressionCompiler);
                     var renderedItems = await templateRenderer.RenderAsync(template.FilePath, templateContent, codeModel, userInput.TypesThatMayContainCustomFunctions, editorConfig, environmentVariables).ConfigureAwait(false);
 
                     await GeneratedFileManager.SaveChanges(renderedItems, generatedFileReaderWriter, uiOutput, sourceControl).ConfigureAwait(false);
diff --git a/NTypewriter.Runtime/Rendering/TemplateRenderer.cs b/NTypewriter.Runtime/Rendering/TemplateRenderer.cs
index 3abf8a5..9922695 100644
--- a/NTypewriter.Runtime/Rendering/TemplateRenderer.cs
+++ b/NTypewriter.Runtime/Rendering/TemplateRenderer.cs
@@ -7,7 +7,6 @@
 using NTypewriter.Editor.Config;
 using NTypewriter.Ports;
 using NTypewriter.Runtime.Rendering.Internals;
-using NTypewriter.Runtime.Scripting;
 
 namespace NTypewriter.Runtime.Rendering
 {
@@ -15,12 +14,13 @@ public class TemplateRenderer
     {
         private readonly IUserInterfaceErrorListUpdater errorList;
         private readonly IUserInterfaceOutputWriter output;
+        private readonly IExpressionCompiler expressionCompiler;
 
-
-        public TemplateRenderer(IUserInterfaceErrorListUpdater errorList, IUserInterfaceOutputWriter output)
+        public TemplateRenderer(IUserInterfaceErrorListUpdater errorList, IUserInterfaceOutputWriter output, IExpressionCompiler expressionCompiler)
         {
             this.errorList = errorList;
             this.output = output;
+            this.expressionCompiler = expressionCompiler;
         }
 
 
@@ -40,7 +40,7 @@ public async Task<IEnumerable<RenderingResult>> RenderAsync(string templateFileP
             dataModels[VariableNames.Config] = configAdapter;
             dataModels[VariableNames.Env] = environmentVariables ?? new EnvironmentVariables();
 
-            var result = await NTypeWriter.Render(template, dataModels, configuration, new ExternalOutputAdapter(output), new ExpressionCompiler());
+            var result = await NTypeWriter.Render(template, dataModels, configuration, new ExternalOutputAdapter(output), expressionCompiler);
 
             output.Info("Used configuration : " + editorConfig.ToString());
 
diff --git a/NTypewriter.Runtime/Scripting/ExpressionCompiler.cs b/NTypewriter.Runtime/Scripting/ExpressionCompiler.cs
index f83f8ee..4210d7b 100644
--- a/NTypewriter.Runtime/Scripting/ExpressionCompiler.cs
+++ b/NTypewriter.Runtime/Scripting/ExpressionCompiler.cs
@@ -11,8 +11,9 @@
 
 namespace NTypewriter.Runtime.Scripting
 {
-    internal class ExpressionCompiler : IExpressionCompiler
+    public class ExpressionCompiler : IExpressionCompiler
     {
+        private static readonly Lazy<ExpressionCompiler> defaultSingleton = new Lazy<ExpressionCompiler>(() => new ExpressionCompiler());
         private static readonly Type[] RefTypeMarkers = 
         [            
             typeof(NTypewriter.CodeModel.ICodeModel),
@@ -24,10 +25,12 @@ internal class ExpressionCompiler : IExpressionCompiler
             "System",
             "NTypewriter.CodeModel",            
         ];
-        private static readonly IEnumerable<MetadataReference> MetadataReferences;
+        private readonly IEnumerable<MetadataReference> MetadataReferences;
 
+        public static ExpressionCompiler Default => defaultSingleton.Value;
 
-        static ExpressionCompiler()
+
+        public ExpressionCompiler()
         {
             var additionalReferences = RefTypeMarkers.Select(x => MetadataReference.CreateFromFile(x.Assembly.Location)).ToList();
 
@@ -37,6 +40,10 @@ static ExpressionCompiler()
 
             MetadataReferences = references;
         }
+        public ExpressionCompiler(IEnumerable<MetadataReference> references)
+        {
+            MetadataReferences = references;
+        }
 
 
         public Func<object, bool> CompilePredicate(string predicate, Type type)