Is it possible to determine in which language a .NET Assembly was written ex post facto?

Question

This started as a way to find C++/CLI and Managed C++ assemblies so that all classes internal to them could be tested to ensure all inherited methods were being reimplemented. I would like to add this as a build process step to ensure that it never happens again.

Thinking about this problem also made me a bit curious as it would be interesting to be able to determine any .NET language used. Because of this, I went a bit further and compared assemblies from all of the .NET languages. So far here is what I've found through a small program I wrote which compares the type and attribute data from any set of .NET assemblies via reflection:

• C# - Has AssemblyConfigurationAttribute, Has GuidAttribute
• VB - Has many extra "My" type (ex. MyApplication, MySettings), Has GuidAttibute
• F# - Has a FSharpInterfaceDataVersionAttribute which also specifies the version of the compiler used.
• C++ (all but /clr:safe) - Has a bunch of extra types (FrameInfo, type_info)
• C++ /clr:safe - Seems to have no unique reflection features.

It might be reasonable to parse in this order:

1. It's F# if it has the FSharpInterfaceDataVersionAttribute
2. It's C++ if it has any in the huge set of extra types I found.
3. It's VB if it has the "My*" Types.
4. It's C# if it has AssemblyConfigurationAttribute or GuidAttribute
5. It's likely to be C++ /clr:Safe

However, as this is a horrible hack, I wanted to check in here to make sure that there wasn't another option available.

Answer 1

When a .NET language is compiled, all you get is IL. I am not aware of a standard way of determining which specific language created the assembly. You can take an existing assembly and ildasm (disassemble) it into IL and them ilasm (assemble) it back into a virtually identical assembly.

The heuristics you use is a reasonable and clever way to identify the language used to create the assembly. However, bear in mind that these details might change between compiler versions of the languages.

Answer 2

Checking the references for things like the VB or F# class libraries seems to be the least shaky way to do this, but as others mention, it's a heuristic - just like there's no definitive way to tell which language a native binary is written in (but you can be almost 100% sure by heuristics)