I hope this is the appropriate forum to ask this question.

A group of colleagues and I just starting learning C# a few weeks ago and we are planning on having a discussion about language interoperability.

So, I am looking for known/classical examples of .Net language interoperability issues. Like this one, where the case-insensitiveness of VB.Net makes an overloaded C# method incompatible.

In C#

public class Foo
    public void foo() { }
    public void fOO() { }

In VB.Net

Public Class Bar
   Sub Bar()
      Dim foo As Foo
      foo = New Foo()
      foo.foo(); //compiler error
   End Sub
End Class

Or this one in which a VB.Net keyword is used in a C# method name:

In C#

public class Foo
   public virtual void Stop() { }

In VB.Net

Public Class Bar
    Inherits Foo

    Public Overrides Sub Stop() 'compiler error
    End Sub

End Class

I would love to gather a few more examples of this type of issues.

Does anyone know any other interesting cases of language interoperability gotchas?

I used C# and VB.Net in these examples, but any .Net language interoperability issue will be just as good to enrich a discussion on the subject.

  • is it the same post? - stackoverflow.com/questions/11691538/…
    – Yusubov
    Jul 27, 2012 at 17:03
  • @ElYusubov Yes, in Stackoverflow it was suggested to me that this question should belong in this forum, and not in SO. I waited till it was closed to reopen it here. Is there a reason why it should not belong here?
    – edalorzo
    Jul 27, 2012 at 17:07
  • OK, no problem. juts wanted to verify. Thx!
    – Yusubov
    Jul 27, 2012 at 17:15
  • 8
    I'd just like to point out that the second example you posted can easily be handled by placing brackets around the keyword, like so: Public Overrides Sub [Stop]()
    – rossipedia
    Jul 27, 2012 at 17:34
  • 1
    Technically, yes. But then again these are the kinds problems that are unavoidable whenever you are crossing the language boundary.
    – rossipedia
    Jul 28, 2012 at 20:13

2 Answers 2


Common Language Specification is a key

It would be better to enhance your understanding of how to write a Common Language Specification (CLS) compliant code. I believe that would resolve most of the issues that you have faced or found.

Basically, CLS compliance refers to CLS rules and restrictions that being followed. However, the concept has a more specific meaning depending on whether you are describing CLS-compliant code or CLS-compliant development tools, such as a compiler. CLS-compliant tools can help you write CLS-compliant code.

enter image description here

There are numerous articles on MSDN and elsewhere that I would suggest to follow:

  • IIRC FxCop has rules to help here
    – jk.
    Jul 27, 2012 at 17:56

Keep in mind that you are not restricted in the code that is internal to your assembly, only things that are exposed publicly need to be CLS compliant.

  • Don't expose unsigned variables.
  • Don't expose identifiers that only differ by case.
  • Operator overloading, some languages can't use overloaded operators, so provide a method to achieve the same function as your overloaded operator.
  • Avoid unmanaged pointers.
  • Keep names unique, for example don't name a types method and field the same thing.
  • Don't expose boxed value types.
  • Don't overload fields or events.
  • Don't overload properties by type.
  • Don't overload methods by return type.
  • Expose alternative methods for implicit and explicit casts.
  • Don't expose variable length argument lists (params keyword in C#).
  • Don't use arrays with a nonzero lower bound (https://stackoverflow.com/a/5733008/279999).
  • Don't throw objects that don't inherit from System.Exception.
  • Mark your assembly with (System.ClsCompliant) attribute.

Not the answer you're looking for? Browse other questions tagged or ask your own question.