NullReferenceException thrown when using CSharpValue

[zh6335901]

Here is sample code:

internal static class Program
{
    static void Main(string[] args)
    {
        var v1 = new Variable<int>();

        var helloWorldActivity = new Sequence()
        {
            Variables = { v1 },
            Activities =
            {
                new WriteLine
                {
                    Text = new CSharpValue<string>("\"aaaa\" + \"sadas\"")
                }
            }
        };

        CompileWorkflow(helloWorldActivity);
        var wfApp = new WorkflowApplication(helloWorldActivity);

        wfApp.Run();

        Console.ReadLine();
    }

    private static void CompileWorkflow(Activity activity)
    {
        var activityName = activity.GetType().ToString();
        var activityType = activityName.Split('.').Last() + "_CompiledExpressionRoot";
        var activityNamespace = string.Join(".", activityName.Split('.').Reverse().Skip(1).Reverse());

        var settings = new TextExpressionCompilerSettings
        {
            Activity = activity,
            Language = "C#",
            ActivityName = activityType,
            ActivityNamespace = activityNamespace,
            RootNamespace = null,
            GenerateAsPartialClass = false,
            AlwaysGenerateSource = true,
            ForImplementation = false,
        };

        TextExpressionCompilerResults results = new TextExpressionCompiler(settings).Compile();

        // Any compilation errors are contained in the CompilerMessages.
        if (results.HasErrors)
            throw new Exception("Compilation failed.");

        // Create an instance of the new compiled expression type.
        var compiledExpressionRoot =
            Activator.CreateInstance(results.ResultType,
                new object[] { activity }) as ICompiledExpressionRoot;

        CompiledExpressionInvoker.SetCompiledExpressionRoot(
            activity, compiledExpressionRoot);
    }
}

The result of running: