private async void LoadCourseDataAsync(Course course) { var fullCourse = await _courseHandler.GetCourse(course.Id); if (fullCourse != null) { DBFiles.Clear(); Lessons.Clear(); foreach (var item in fullCourse.CourseMaterials) { DBFiles.Add(item); } foreach (var item in fullCourse.Lessons) { Lessons.Add(item); } CurrentSemester = course.Semester; } }