Compiler Error CS0061

Inconsistent accessibility: base interface 'interface 1' is less accessible than interface 'interface 2'

A public construct must return a publicly accessible object.

Interface accessibility cannot be narrowed in a derived interface. For more information, see Interfaces and Access Modifiers.

The following sample generates CS0061.

// CS0061.cs  
// compile with: /target:library  
internal interface A {}  
public interface AA : A {}  // CS0061  
  
// OK  
public interface B {}  
internal interface BB : B {}  
  
internal interface C {}  
internal interface CC : C {}