Reading .NET 4 assemblies from codesmith Template
Although CodeSmith future version will support .NET 4 out of box, current version does not support it directly. If your template needs to read from a .NET 4 assembly, embed start-up element in your CodeSmith config files (Configuration files are located on the Installation folder).
<startup> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> </startup>
If you want to use .NET 4 features in your templates, you can change from CompilerVersion=”v3.5″ to CompilerVersion=”v4.0″