c# linq查询

List<DeptInfo> deptList = (from emp in empList
                                where emp.Status == "在职"            //筛选“在职”员工     
                                orderby emp.DeptID ascending          //按“部门ID”排序
                                group emp by new                      //按“部门ID”和“部门名称”分组
                                {
                                    emp.DeptID,
                                    emp.DeptName
                                }
                                into g
                                select new DeptInfo()
                                {
                                    DeptID = g.Key.DeptID,
                                    DeptName = g.Key.DeptName,
                                    EmplayeeCount = g.Count(),          //统计部门员工数量
                                    WageSum = g.Sum(a => a.Wage),       //统计部门工资总额
                                    WageAvg = g.Average(a => a.Wage),   //统计部门平均工资
                                    EmplayeeList = (from e in g         //归集部门员工列表
                                                    select new Emplayee()
                                                    {
                                                        EmpID = e.EmpID,
                                                        EmpName = e.EmpName
                                                    }
                                                    ).ToList()
 
                                }).ToList();
 

 拼接分组后的字符：

1：

var result = from item in tbl
 group item by item.name into g
let ids = g.Select(b => b.id.ToString()).ToArray()
 select new { id = String.Join(",", ids), name = g.Key };

:2：

var tbl2 = from item in db.tbl select new {id=item.id.ToString(),item.name };

var result = from item in tbl2

    group item by item.name into g

    select g.Aggregate(

        (workingSentence, next) => 

            new { 
　　　　　　　　　　ids =workingSentence.id + "," +next.id  , name = g.Key 
　　　　　　　　　　}
　　);

 //分组 求和

 var temp = (from a in student
                            from p in syncchip
                                //  join p in syncchip
                                //on c.id equals p.user_id
                            where a.class_id == index
                            orderby a.id
                            group new {a.id,a.name,a.className,a.sex ,a.head_img, p.user_id }
                            by new { a.id, a.name, a.className, a.sex, a.head_img} into g                            
                            select new
                            {
                                stdent_id = g.Key.id,
                                name = g.Key.name,
                                className = g.Key.className,
                                sex = g.Key.sex,
                                head_img = g.Key.head_img,
                                cou= g.Count(c => c.user_id== g.Key.id)                                                 
                            }).ToList();

var temp = (from a in student
                            from p in syncchip
                                //  join p in syncchip
                                //on c.id equals p.user_id
                                where a.class_id==index
                                orderby a.id
                                group a by new { a.id,a.name,a.className ,a.sex,a.head_img } into g

                            select new
                            {
                                stdent_id =g.Key.id,
                                name = g.Key.name,
                                className = g.Key.className,
                                sex = g.Key.sex,
                                head_img=g.Key.head_img,
                                cou = (from e in syncchip        
                                       where e.user_id == g.Key.id
                                       group e by e.user_id into b
                                       select new
                                       {
                                           cou = g.Count()
                                       }
                                       ).Count()                                
                            }).ToList();

                List<StudentClass> list = new List<StudentClass>();
                foreach (var i in temp)
                {
                    list.Add(new StudentClass {student_id =i.stdent_id,name=i.name,cou=i.cou ,className=i.className,sex=i.sex,head_img=i.head_img});
                }

var temp = (from a in Waybills
                        from p in PlanOrders
                        where a.PlanId == p.Id
                        orderby a.SendTime
                        group  a
                        by new { a.ProId ,a.ProName, a.GmId, a.GmName, a.GmModel, p.PlanNumber } into g
                        select  new
                        {
                            Time= teme.ToString(),
                            Type="当日汇总",
                            ProId = g.Key.ProId,
                            Id= g.FirstOrDefault().Id,
                            PlanId = g.FirstOrDefault().PlanId,
                            ProName = g.Key.ProName,
                            GmId = g.Key.GmId,
                            GmName = g.Key.GmName,
                            GmModel = g.Key.GmModel,
                            //计划数量
                            PlanNumber=g.Key.PlanNumber,
                            //完成数量
                            Sum = g.Sum(a => a.LoadingWeight),
                            //完成率                            
                            CompletionRate = decimal.Round(((g.Sum(a => a.LoadingWeight) / g.Key.PlanNumber) * 100),2),
                            //派车数量
                            cou=g.Count(),
                            //完成车数
                            Complete = g.Count(a => a.Status==2)
                            //备注


                        }).ToList();