如何在 asp.net 中的新闻中获取类别计数

Question

大家好，我在获取新闻中类别使用的数量时遇到问题

例如，我想知道“国际”类别在新闻中有多少使用

这是我的新闻实体：

 public class News
    {
        public int NewsId { get; set; }
       
        public int? SubGroup { get; set; }

        public string NewsTitle { get; set; }
        public string NewsBody { get; set; }
        public DateTime CreatedDate { get; set; }
        public string Poster { get; set; }
       
        public DateTime? UpdateTime { get; set; }
        public bool  isChoseClerck{ get; set; }

        public News()
        {
            this.CreatedDate = DateTime.Now;
        }

        //RelationShip
        public List<Category>  Category { get; set; }
        public User User { get; set; }
        public List<Tag> Tags { get; set; }
        public string Source{ get; set; }
    }

这是我想向用户展示的 Dto：

 public class SubCategoryWithCountDTO
    {
        public int CategoryId { get; set; }
        public string CateGoryName { get; set; }
        public int UseCount { get; set; }
    }

我在服务下面写过我不知道我不能在“包含”中使用 lambda

 public async Task<List<SubCategoryWithCountDTO>> SubCategoryWithCount(int skip, int take)
        {
            var subCategoryList = await _context.Categories
                .Where(x => x.ParentId != null).OrderBy(x => x.CategoryId)
                .Skip(skip).Take(take).ToListAsync();
            var SubCategoryWithCount = new List<SubCategoryWithCountDTO>();
            foreach (var item in subCategoryList)
            {
                var categoryUse = _context.News.Include(x => x.Category
                    .Select(x => x.CategoryId == item.CategoryId)).Count();
                var preSubCategory = new SubCategoryWithCountDTO
                {
                    CategoryId = item.CategoryId,
                    CateGoryName = item.CateGoryName,
                    UseCount = categoryUse
                };
                SubCategoryWithCount.Add(preSubCategory);
            }

            return SubCategoryWithCount;
        }

有人可以告诉我正确的方法吗？谢谢

Answer 1

我对我的服务进行了一些更改，并使用了其他一些方法来计算，是的，它确实有效

  public async Task<List<SubCategoryWithCountDTO>> SubCategoryWithCount(int skip, int take)
        {
            var subCategoryList = await _context.Categories
                .Where(x => x.ParentId != null).OrderBy(x => x.CategoryId)
                .Skip(skip).Take(take).ToListAsync();
            var SubCategoryWithCount = new List<SubCategoryWithCountDTO>();

            var news = _context.News.Include(x => x.Category);
            foreach (var item in subCategoryList)
            {

                var categoryUse = news.SelectMany(x => x.Category.Where(x => x.CategoryId == item.CategoryId)).CountAsync();
                var preSubCategory = new SubCategoryWithCountDTO
                {
                    CategoryId = item.CategoryId,
                    CateGoryName = item.CateGoryName,
                    UseCount = await categoryUse
                };
                SubCategoryWithCount.Add(preSubCategory);
            }

            return SubCategoryWithCount;
        }