Compiler Warning (level 1) CS3009


Updated: July 20, 2015

For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

'type': base type 'type' is not CLS-compliant

A base type was marked as not having to be compliant with the Common Language Specification (CLS) in an assembly that was marked as being CLS compliant. Either remove the attribute that specifies the assembly is CLS compliant or remove the attribute that indicates the type is not CLS compliant. For more information on CLS Compliance, see Writing CLS-Compliant Code and Language Independence and Language-Independent Components.

The following example generates CS3009:

// CS3009.cs  
using System;  
public class B  
public class C : B   // CS3009  
    public static void Main () {}