1，求和
var datas = SellOutActualData.Where(b => b.BrandCode == brandExportParam.BrandInfo.BrandCode && b.ReportMonth == item.Month);
decimal sumValue = datas.Sum(a => a.Amount);
2，Linq筛选，转换成指定类
var query = dbContext.TWSalesRecord.Where(d => d.DataSource == "HCT");
//筛选字段HCTAccount中的值要在 model.AccountList内
query = query.Where(d => model.AccountList.Contains(d.HCTAccount));
List<TWSalesData> data = query.Where(d => d.ReportMonth >= model.StartDate
&& d.ReportMonth <= model.EndDate
&& !string.IsNullOrEmpty(d.GSKGMMCode))
.Select(d => new TWSalesData
{
Account = d.HCTAccount,
GMMCode = d.GSKGMMCode,
ReportMonth = d.ReportMonth,
Amount = d.GSKAmount
}).ToList(); //将最终的结果转为Sales类集合
3，linq筛选，转换成 “字典”
private Dictionary<string, TWProducts> products = new Dictionary<string, TWProducts>(); products = db.TWProducts.ToDictionary(d => d.GMMCode, d => d);
4，分组查询
结果是，某个分销商，在某月中的 某个商品的 “总销售额” 和 “数量” 是多少
List<SalesDataModel> sales = (from data in db.TWSalesRecord
group data by new
{
data.HCTAccount, //根据分销商，月份，商品编码分组
data.ReportMonth,
data.GSKGMMCode
} into d
select new SalesDataModel
{
Account = d.Select(s => s.HCTAccount).FirstOrDefault(),
Month = d.Select(s => s.ReportMonth).FirstOrDefault(),
GMMCode = d.Select(s => s.GSKGMMCode).FirstOrDefault(),
Value = d.Sum(s => s.GSKAmount)/,
Quantity = d.Sum(s => s.Quantity)
}).ToList();
5，简单计算函数（sum，max，min，count）
//linq
Var ss=(from r in db.table select r).max(p=>p.id);
.min(p=>p.id);
.sum(p=>p.id);
.count();
//Lambda
Var ss1=db.table.max(p=>p.id);
Var ss1=db.table.min(p=>p.id);
Var ss1=db.table.sum(p=>p.id);
Var ss1=db.table.count();