lambda 表达式分组，分页与linq 分组查询语句

最新推荐文章于 2024-06-25 22:46:06 发布

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最新推荐文章于 2024-06-25 22:46:06 发布

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CC 4.0 BY-SA版权

文章标签：数据库

原文链接：http://www.cnblogs.com/xust/articles/2876786.html

本文介绍了如何使用Lambda表达式对组织机构数据进行分组和分页查询，通过设置查询参数、分页参数以及排序参数来实现数据的有效筛选和展示。

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        // lambda 表达式 分组，并且分页
　　　　　/// <summary>
        /// 获取所有组织机构数据(按价格名称分组)
        /// </summary>
        /// <returns></returns>
        public string PriceStandardSelectAllGroupBy()
        {
            IList<PriceStandard> mPriceStandards = new List<PriceStandard>();
            IList<PriceStandard> mGroupPriceStandards = new List<PriceStandard>();
            int mTotal = 0;
            int mStart = 0;
            int mLimt = 0;
            if (Request.Params["id"] != null && !string.IsNullOrEmpty(Request.Params["id"].ToString()))
            {
                mPriceStandards.Add(PriceStandardSrv.GetById(Request.Params["id"].ToString()));
                mTotal = 1;
            }
            else
            {
                // 设置查询参数
                var mConditions = new PriceStandard();
                TryUpdateModel(mConditions);

                // 设置分页参数
                mStart = int.Parse(Request.Params["start"]);
                mLimt = int.Parse(Request.Params["limit"]);
                mConditions.rowStart = mStart + 1;
                mConditions.rowEnd = mStart + mLimt;

                // 设置排序参数
                if (!string.IsNullOrEmpty(Request.Params["sort"]))
                {
                    mConditions.sorts = JsonConvert.DeserializeObject<List<Sort>>(Request.Params["sort"]);
                }
                else
                {
                    mConditions.sorts = new List<Sort>() { new Sort() { property = "id", direction = "DESC" } };
                }

                mPriceStandards = PriceStandardSrv.SelectAll();
                mGroupPriceStandards = mPriceStandards
                    .GroupBy(m => new { m.priceName })
                    .Select(g => new PriceStandard
                    {
                        priceName = g.Key.priceName,
                    }).ToList<PriceStandard>();

                mTotal = mGroupPriceStandards.Count();
                mGroupPriceStandards = mGroupPriceStandards
                            .Skip(mStart * mLimt)
                            .Take(mLimt)
                            .ToList<PriceStandard>();
            }

            var output = JsonConvert.SerializeObject(mGroupPriceStandards, new IsoDateTimeConverter());
            var returnStr = @"{
                success: true,
                total: " + mTotal.ToString() + @",
                data: " + output + @"}";
            return returnStr;
        }

        //linq 分组
        IList<PriceStandard> mGroupPriceStandards = new List<PriceStandard>();
        mGroupPriceStandards = (from m in mPriceStandards
                        group m by new { m.priceName, m.salesTypeName } into g
                        select new PriceStandard
                        {
                             priceName = g.Key.priceName,
                             salesTypeName = g.Key.salesTypeName
                        }).ToList<PriceStandard>();