'member' is external and has a body
When a class member is marked extern, it means that the member's definition is located in another file. Therefore, a class member marked as extern cannot be defined in the class. Either remove the extern keyword or delete the definition.
The following sample generates CS0179:
public class MyClass { public extern int ExternMethod(int aa) { // CS0179 return 0; } // try the following line instead // public extern int ExternMethod(int aa); public static void Main() { } }