如何使用LINQ C＃过滤列表

Question

我需要将List<Students>过滤成StudentsWitHighestDebts 。

标准是只有ZachetDidNotPass在所有List<Students>中具有最大值和maximum-1 List<Students>才会包含在结果中。

var StudentsWitHighestDebts = students
               .Where(s => s.ZachetDidNotPass.(some condition))
               .OrderBy(s => s.Name)
               .ToList();

例如，给出具有ZachetDidNotPass值0 1 2 5 6 7的学生列表。 生成的StudentsWitHighestDebts应该只包含ZachetDidNotPass具有7 and 6值的ZachetDidNotPass 。

Answer 1

第一种选择：承担2笔最高债务并按ZachetDidNotPass筛选学生：

var highestDebts = students.Select(s => s.ZachetDidNotPass)
    .OrderByDescending(p => p).Take(2).ToArray();
var studentsWitHighestDebts = students
    .Where(s => highestDebts.Contains(s.ZachetDidNotPass))
    .OrderByDescending(s => s.ZachetDidNotPass).ToList();

第二个选项 - 按ZachetDidNotPass分组，按键降序排序组，前2个组并从组中选择学生

var studentsWitHighestDebts = students.GroupBy(s => s.ZachetDidNotPass)
    .OrderByDescending(g => g.Key).Take(2)
    .SelectMany(g => g).ToList();

第三种选择（以最高债务和最高债务的学生 - 1）

var highestDebt = students.Max(s => s.ZachetDidNotPass);

var studentsWitHighestDebts = students
    .Where(s => s.ZachetDidNotPass == highestDebt || s.ZachetDidNotPass == highestDebt - 1)
    .OrderByDescending(s => s.ZachetDidNotPass).ToList();