LINQ使用Orderby、ThenBy实现多字段的排序

系统管理员 2021-09-16 22:28 583阅读 0赞

LINQ中的排序操作符，包括：OrderBy、OrderByDescending、ThenBy、ThenByDescending、Reverse，提供了升序或者降序排序。  
OrderBy：按升序对序列的元素进行排序。  
OrderByDescending：按降序对序列的元素排序。  
ThenBy：按升序对序列中的元素执行后续排序。  
ThenByDescending：按降序对序列中的元素执行后续排序。  
Reverse：反转序列中元素的顺序。

**示例：**将员工列表进行排序，排序要求：  
1、按部门编号升序；  
2、按员工薪资降序；  
3、按员工入职时间升序；

**方式一：**

empList = empList.OrderBy(a => a.DeptID).ThenByDescending(a => a.Salary).ThenBy(a => a.EntryTime).ToList();

**方式二：**

empList = (from emp in empList
                orderby emp.DeptID ascending,
                emp.Salary descending,
                emp.EntryTime ascending
                select emp).ToList();

**完整代码：**

static void Main(string[] args)
    {
        //获取员工列表
        List<Employee> empList = GetEmployeeList();
    
        //打印排序前列表
        System.Console.WriteLine("排序前：");
        empList.ForEach(a => System.Console.WriteLine(a.ToString()));
    
        //使用LINQ执行排序
        empList = empList.OrderBy(a => a.DeptID).ThenByDescending(a => a.Salary).ThenBy(a => a.EntryTime).ToList();
    
        //打印排序后列表
        System.Console.WriteLine("");
        System.Console.WriteLine("排序后：");
        empList.ForEach(a => System.Console.WriteLine(a.ToString()));
        System.Console.ReadLine();
    }
    
    /// <summary>
    /// 获取员工列表
    /// </summary>
    public static List<Employee> GetEmployeeList()
    {
        List<Employee> result = new List<Employee>();
        result.Add(new Employee() { Name = "张伟伟", DeptID = 3, DeptName = "市场部", Salary = 1500, EntryTime = DateTime.Parse("2016-05-12")});
        result.Add(new Employee() { Name = "李涛涛", DeptID = 2, DeptName = "财务部", Salary = 1600, EntryTime = DateTime.Parse("2017-02-16") });
        result.Add(new Employee() { Name = "王亮亮", DeptID = 1, DeptName = "研发部", Salary = 1900, EntryTime = DateTime.Parse("2018-10-25") });
        result.Add(new Employee() { Name = "孙红红", DeptID = 1, DeptName = "研发部", Salary = 1900, EntryTime = DateTime.Parse("2018-08-03") });
        result.Add(new Employee() { Name = "黄苗苗", DeptID = 3, DeptName = "市场部", Salary = 2200, EntryTime = DateTime.Parse("2016-09-06") });
        result.Add(new Employee() { Name = "蔡明明", DeptID = 1, DeptName = "研发部", Salary = 3500, EntryTime = DateTime.Parse("2012-11-25") });
        result.Add(new Employee() { Name = "吴慧慧", DeptID = 2, DeptName = "财务部", Salary = 1800, EntryTime = DateTime.Parse("2018-07-26") });
        result.Add(new Employee() { Name = "杨梅梅", DeptID = 3, DeptName = "市场部", Salary = 2200, EntryTime = DateTime.Parse("2017-02-15") });
        return result;
    }

创建员工信息类（Emplayee.cs）

/// <summary>
    /// 员工信息类
    /// </summary>
    public class Employee
    {
        /// <summary>
        /// 员工名称
        /// </summary>
        public string Name { get; set; }
    
        /// <summary>
        /// 部门编号
        /// </summary>
        public int DeptID { get; set; }
    
        /// <summary>
        /// 部门名称
        /// </summary>
        public string DeptName { get; set; }
    
        /// <summary>
        /// 薪资
        /// </summary>
        public decimal Salary { get; set; }
    
        /// <summary>
        /// 入职时间
        /// </summary>
        public DateTime EntryTime { get; set; }
    
        public override string ToString()
        {
            return String.Format("{0}；{1}；薪资：{2}元；入职时间：{3}；", this.Name, this.DeptName, this.Salary, this.EntryTime.ToString("yyyy-MM-dd"));
        }
    }

执行结果如下图：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bhbl9qdW5iaWFv_size_16_color_FFFFFF_t_70][]

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