使用 LINQ/Lambda 查找员工的第 N 个最高薪水

Question

Hi I used sequential Linq for getting nth highest salary from employee like

    var ThirdHighestSal = from vr in Employee.getAllEmployee()
                 group vr by vr.Salary into gr
                 orderby gr.Key descending
                 select( new {salary=gr.OrderBy(x=>x.Salary).Skip(2).First()});
        foreach (var sal in ThirdHighestSal)
        {
            Console.WriteLine("3rd highest sal is {0}",sal.salary);
        }

when i execute this it is throwing exception like

Sequence contains no elements(InvalidOperationException was unhadled)

Can anyone help me on that query please?

Answer 1

use FirstOrDefault instead of First and you will get a null object if no element could be found.

With lamda you could write:

 var ThirdHighestSal = Employee.getAllEmployee().Select(x => x.Salary).Distinct().OrderByDescending(x => x).Skip(2).FirstOrDefault();

Then you get null or (if exists) the third highest salary.

Answer 2

var employees = Employees
    .GroupBy(e => e.Salary)
    .OrderByDescending(g => g.Key)
    .Skip(N-1)
    .First();