Linq to sql 语法方法示例

联表查询，判断追加条件，对集合分页

 public ActionResult Index(string titleName, string nickName, int pageIndex = 1)
        {
            var data = from m in _db.AppArticleComment
                       join o in _db.AppArticle on m.ArticleId equals o.ArticleId
                       where (string.IsNullOrEmpty(nickName) ? true : m.NickName == nickName)//在此判断加条件，当变量值null需要转为整型时会抱异常
                       select new AppArticleCommentModel()
                       {
                           Id = m.Id,
                           OId = m.OId,
                           MId = m.MId,
                           NickName = m.NickName,
                           Comment = m.Comment,
                           Good = m.Good,
                           Created = m.Created,
                           IsHorizontal = m.IsHorizontal,
                           Version = m.Version,
                           From = m.From,
                           ArticleName = o.Title

                       };

            if (!string.IsNullOrEmpty(titleName))
            {
                //也可在此判断添追加条件
                data = data.Where(m => m.ArticleName.Contains(titleName)); 
            }

            int total = 0;
            int pageSize = 10;
            //对集合进行分页
            var query = data.OrderByDescending(m => m.Created)
                .Skip(pageSize * (pageIndex - 1)).Take(pageSize);

            var list = query.ToList();
            total = data.Count();

            PagingHelper<AppArticleCommentModel> dataPaging = new PagingHelper<AppArticleCommentModel>(10, list);//初始化分页器
            dataPaging.PageIndex = pageIndex;//指定当前页
            dataPaging.PageCount = (int)Math.Ceiling(total / (double)pageSize);
            dataPaging.PageSize = pageSize;
            dataPaging.TotalCount = total;

            return View(dataPaging);//返回分页器实例到视图
        }