foo1.cs

      protected override IRearrangeable CreateElement(IMultipleDeclarationMember member)
      {
        IMultipleDeclaration parent = null;
        string title = "declaration";

        if (member is IFieldDeclaration)
        {
          parent = MultipleFieldDeclarationNavigator.GetByDeclarator((IFieldDeclaration)member);
          title = "field";
        }
        else if (member is IEventDeclaration)
        {
          parent = MultipleEventDeclarationNavigator.GetByDeclarator((IEventDeclaration)member);
          title = "event";
        }
        else if (member is IConstantDeclaration)
        {
          parent = MultipleConstantDeclarationNavigator.GetByDeclarator((IConstantDeclaration)member);
          title = "constant";
        }

        return parent != null ? new RearrangeableDeclaration(member, parent, title) : null;
      }

foo2.cs

      protected override IRearrangeable CreateElement(IMultipleDeclarationMember member)
      {
        IMultipleDeclaration parent = null;
        string title = "declaration";

        if (member is IFieldDeclaration fieldDeclaration)
        {
          parent = MultipleFieldDeclarationNavigator.GetByDeclarator(fieldDeclaration);
          title = "field";
        }
        else if (member is IEventDeclaration eventDeclaration)
        {
          parent = MultipleEventDeclarationNavigator.GetByDeclarator(eventDeclaration);
          title = "event";
        }
        else if (member is IConstantDeclaration constantDeclaration)
        {
          parent = MultipleConstantDeclarationNavigator.GetByDeclarator(constantDeclaration);
          title = "constant";
        }

        return parent != null ? new RearrangeableDeclaration(member, parent, title) : null;
      }