Question

我有Employee列表

EmpId EmpName ManagerId Salary

ManagerId是EmpId

之一

我想从同一个列表中获取EmpName，ManagerName（使用ManagerId获取EmpName）。请任何人帮助我..

List<Employee> emp = new List<Employee>();
emp.Add(new Employee() { Empid = 1, EmpName = "Arivu", Managerid=null, salary = 20000 });
emp.Add(new Employee() { Empid = 2, EmpName = "kavi", Managerid=1, salary = 30000 });
emp.Add(new Employee() { Empid = 6, EmpName = "karthi", Managerid = 1, salary = 307000 });
emp.Add(new Employee() { Empid = 3, EmpName = "Anbu", Managerid = 2, salary = 40000 });
emp.Add(new Employee() { Empid = 4, EmpName = "asfdsf", Managerid = 1, salary = 55000 });
emp.Add(new Employee() { Empid = 5, EmpName = "Nithya", Managerid = 3, salary = 12000 });

这是列表，我想从empname列表中获取managername和emp

Answer 1

var result = from emp in empList 
             join mng in empList on emp.ManagerId equals mng.Id
             select new { 
                           emp.EmpName,
                           ManagerName =  mng.EmpName 
                         };

或

var result = empList.Join(empList , emp => emp.ManagerId, mng => mng.EmpId, (emp, mng) => new
            {
                emp.EmpName,
                ManagerName = mng.EmpName
            });

Answer 2

我经常尝试避免SelectMany查询，因为它们并不总是最具可读性。因此，根据具体情况，我可能会这样做：

var map = emp.ToDictionary(e => (int?)e.Empid);

Func<int?, string> getNameFromId = i =>
    i == null ? "n/a" : map[i].EmpName;

var query =
    from e in emp
    select new
    {
        e.EmpName,
        ManagerName = getNameFromId(e.Managerid)
    };

我发现这种事情更加明确，特别是因为当某人没有经理时，它明确地处理了这种情况。

linq中的自联接查询

2 个答案: