Linq 分组实现List<T>到 List<List<T>>

            var list = new List<Course>() {
             new Course(1,"art"),
             new Course(2,"art"),
             new Course(3,"history"),
             new Course(1,"history"),
             new Course(3,"physics")
            };
            var res=list.GroupBy(x => x.stId).Select(x => new { x.Key, names = x.AsEnumerable().Select(g=>g.CourseName).ToArray() }).ToList();

　实现效果如下图