Question

我得到了这个从数据库中读取员工数据的应用程序，只有员工的老板设置在employee_id而不是名字中的问题，这就是我正在寻找的。

我得到了一份满是所有员工的名单。所以我正在寻找一种方法，通过列表查询LINQ，将employee_id链接到名字/姓氏。

示例：身份证号为1的员工是南希，她的老板是安德鲁，但它没有说安德鲁说它2.但应该说安德鲁

我还在下面添加了2张图片，以添加到我的解释中。

Reading out the list of employees into the ListView

Answer 1

所以你需要左加入 ID和Boss并获得Boss信息如果找到：

var employees = Database.getEmployees();

var employeesWithBoss = (from e in employees
                        join b in employees
                        on e.ID equals b.Boss into leftJoin
                        from boss in leftJoin.DefaultIfEmpty()
                        select new
                        {
                            Employee = e,
                            BossFirstName = boss == null ? null : boss.FirstName,
                            BossLastName = boss == null ? null : boss.LastName          
                        }).ToList();

foreach (var employee in employeesWithBoss)
{
    // do your normal work here, you now
    // have employee.BossFirstName and employee.BossLastName
}

Answer 2

首先，将员工加载到一些局部变量中（稍后您将需要它）：

List<Employee> employees = Database.getEmployees();

然后编辑您的foreach周期：

// 'employee' is better because here it is really just one specific employee
foreach (Employee employee in employees)

现在你可以像这样得到老板的名字（在foreach循环中）：

string boss = employees.FirstOrDefault(x => x.ID == employee.ReportsTo)?.FirstName;

（?运算符至少需要C＃6.0。）

Answer 3

你可以使用lambda来实现这一点。

class Program
{
    static void Main(string[] args)
    {
        List<Employee> employees = new List<Employee>();
        employees.Add(new Employee() { EmployeeName = "Nancy", EmployeeId = 1, BossId = 2 });
        employees.Add(new Employee() { EmployeeName = "Andrew", EmployeeId = 2, BossId = 0 });
        employees.Add(new Employee() { EmployeeName = "Janet", EmployeeId = 1, BossId = 2 });

        var employeesWithBossName = employees.Join(employees,
             emp1 => emp1.BossId,
             emp2 => emp2.EmployeeId,
             (emp1, emp2) => new { EmployeeName = emp1.EmployeeName, BossName = emp2.EmployeeName });

        foreach (var item in employeesWithBossName)
        {
            Console.WriteLine("{0} {1}", item.EmployeeName, item.BossName);
        }
        Console.Read();
    }
}

public class Employee
{
    public int EmployeeId { get; set; }
    public string EmployeeName { get; set; }
    public int BossId { get; set; }
}

希望这会有所帮助。

C＃ - 列出＆lt;＆gt;将ID链接到名称

3 个答案: