LINQ 使用group实现多字段的分组

原文：https://blog.csdn.net/pan_junbiao/article/details/79968226

 
    //归集每个部门信息
    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();