internal CourseCategory_Filter[] SingleCourseCategoryFilter(string criteria, CourseCategory_Fields field)
 {
     return(new CourseCategory_Filter[]
     {
         new CourseCategory_Filter()
         {
             Field = field,
             Criteria = criteria
         }
     });
 }
 internal CourseCategory_Filter[] ExtendCourseCategoryFilter(CourseCategory_Filter[] filter, string criteria, CourseCategory_Fields field)
 {
     return(filter.Concat(SingleCourseCategoryFilter(criteria, field)).ToArray());
 }