DefaultInterfaceMethod_usage.cs

  interface IDeveloper
  {
      void LearnNewLanguage(string language, DateTime dueDate);
      void LearnNewLanguage(string language)
      {
          // default implementation
          LearnNewLanguage(language, DateTime.Now.AddMonths(6));
      }
  }

  class BackendDev : IDeveloper // compiles OK
  {
      public void LearnNewLanguage(string language, DateTime dueDate)
      {
          // Learning new language...
      }
  }
  
  class Program
  {
      static void Main(string[] args)
      {
          IDeveloper dev = new BackendDev();
          dev.LearnNewLanguage("Rust"); // OK - default implementation of
                                        // IDeveloper.LearnNewLanguage(string language) is called
      }
  }