LINQ使用group实现多字段的分组

港控/mmm° 2021-09-15 06:14 653阅读 0赞

实例：使用LINQ中group对员工列表进行分组并归集每个部门的信息（如图一）。

要求：1、归集每个部门的详细信息。

2、统计每个部门的员工数量、工资总额、平均工资。

3、归集每个部门下的员工列表。

![2018041623122960][]

图一：结果图

static void Main(string[] args)
    {
        //获取所以员工信息列表
        List<Emplayee> empList = GetAllEmplayeeList();
    
        //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();
    
        //打印结果
        foreach (DeptInfo dept in deptList)
        {
            string msg = String.Format("{0}【员工总数：{1}，工资总额：{2}，平均工资：{3}，员工列表：{4}】",
                dept.DeptName, dept.EmplayeeCount, dept.WageSum, dept.WageAvg, String.Join("、", dept.EmplayeeList.Select(a => a.EmpName)));
            Console.WriteLine(msg);
        }
    
        Console.Read();
    }
    
    /// <summary>
    /// 获取所以员工信息列表
    /// </summary>
    public static List<Emplayee> GetAllEmplayeeList()
    {
        List<Emplayee> empList = new List<Emplayee>();
        empList.Add(new Emplayee() { EmpID = 1, EmpName = "张伟伟", Status = "在职", Wage = 500, DeptID = 1, DeptName = "研发部" });
        empList.Add(new Emplayee() { EmpID = 2, EmpName = "李涛涛", Status = "在职", Wage = 800, DeptID = 1, DeptName = "研发部" });
        empList.Add(new Emplayee() { EmpID = 3, EmpName = "王亮亮", Status = "离职", Wage = 600, DeptID = 1, DeptName = "研发部" });
        empList.Add(new Emplayee() { EmpID = 4, EmpName = "孙红红", Status = "在职", Wage = 400, DeptID = 2, DeptName = "财务部" });
        empList.Add(new Emplayee() { EmpID = 5, EmpName = "黄苗苗", Status = "在职", Wage = 300, DeptID = 2, DeptName = "财务部" });
        empList.Add(new Emplayee() { EmpID = 6, EmpName = "蔡明明", Status = "在职", Wage = 900, DeptID = 3, DeptName = "公共市场部" });
        empList.Add(new Emplayee() { EmpID = 7, EmpName = "吴慧慧", Status = "离职", Wage = 200, DeptID = 3, DeptName = "公共市场部" });
        return empList;
    }

其它代码：

创建员工信息类（Emplayee.cs）

/// <summary>  
    /// 员工信息类  
    /// </summary>  
    public class Emplayee
    {
        /// <summary>
        /// 员工ID
        /// </summary>
        public int EmpID { get; set; }
    
        /// <summary>
        /// 员工名称
        /// </summary>
        public string EmpName { get; set; }
    
        /// <summary>
        /// 状态（在职，离职）
        /// </summary>
        public string Status { get; set; }
    
        /// <summary>
        /// 工资
        /// </summary>
        public decimal Wage { get; set; }
    
        /// <summary>
        /// 部门ID
        /// </summary>
        public int DeptID { get; set; }
    
        /// <summary>
        /// 部门ID
        /// </summary>
        public string DeptName { get; set; }
    }

创建部门信息类（DeptInfo.cs）

/// <summary>
    /// 部门信息类
    /// </summary>
    public class DeptInfo
    {
        /// <summary>
        /// 部门ID
        /// </summary>
        public int DeptID { get; set; }
    
        /// <summary>
        /// 部门ID
        /// </summary>
        public string DeptName { get; set; }
    
        /// <summary>
        /// 员工数量
        /// </summary>
        public int EmplayeeCount { get; set; }
    
        /// <summary>
        /// 工资总额
        /// </summary>
        public decimal WageSum { get; set; }
    
        /// <summary>
        /// 平均工资
        /// </summary>
        public decimal WageAvg { get; set; }
    
        /// <summary>
        /// 员工列表
        /// </summary>
        public List<Emplayee> EmplayeeList { get; set; }
    }

[2018041623122960]: /images/20210724/4f6df66ed2244aa8994baa6df9a7c3b0.png