Using CSharpScript with .NET Standard

Feb 7, 2017  

I expected CSharpScript found in Microsoft.CodeAnalysis.CSharp.Scripting to work with .NET Standard out of the box. But this was not the case. Trying to compile the simplest of code snippets (e.g. returning x+42m, where x is defined in some global type structure) failed:

var options = ScriptOptions.Default;
var script  = CSharpScript.Create<decimal> ("x+42m", options: options, globalsType: typeof (Globals));
var func    = script.CreateDelegate ();

This code resides in an assembly defined as a class library targeting .NET Standard 1.3 and is called from a .NET 4.6.2 console application. When executed, CreateDelegate() throws:

(1,1): error CS0012: The type ‘Decimal’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘System.Runtime, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’.


For this code to work, the ScriptOptions need to be configured in order to include references to some system assemblies:

  • A reference to mscorlib.dll.
  • A reference to the loaded System.Runtime.dll
  • A reference to System.Threading.Tasks.dll if async code needs to be generated.

This is done by calling AddReferences() with the MetadataReference taken from the file paths:

var options = ScriptOptions.Default
    .AddReferences (
        MetadataReference.CreateFromFile (typeof (object).GetAssemblyLoadPath ()),
        MetadataReference.CreateFromFile (TypeExtensions.GetSystemAssemblyPathByName ("System.Threading.Tasks.dll")),
        MetadataReference.CreateFromFile (TypeExtensions.GetSystemAssemblyPathByName ("System.Runtime.dll")));

The TypeExtensions class is defined as:

public static class TypeExtensions
    public static string GetAssemblyLoadPath(this System.Type type)
        return ServiceLocator.AssemblyLoader.GetAssemblyLoadPath (type.GetTypeInfo ().Assembly);

    public static string GetSystemAssemblyPathByName(string assemblyName)
        var root = System.IO.Path.GetDirectoryName (typeof (object).GetAssemblyLoadPath ());
        return System.IO.Path.Combine (root, assemblyName);

Note: we need to specify the absolute path to the assemblies found on disk for this to work.

Edit 1: the ServiceLocator.AssemblyLoader.GetAssemblyLoadPath() function is basically just returning assembly.Location and belongs to code implemented in an IoC container implemented by our framework.

Edit 2: the root of the problem is with Globals being defined in a third assembly, implemented as a .NET Framwork portable class library as my GitHub Code Sample demonstrates.