Question

我需要：

一个list(of employee)，其中包含所有公司中包含的所有员工。（e1，e2 ... e9）
员工的最高离职日期如何高于1/1/2018

我已经以这种方式解决了它，但是我认为可以以更清晰，更有效的方式实现它。也许使用Linq或/和一些lambda表达式

1：

     Dim allEmp As New List(Of employee)
        For Each co In Comps
            For Each emplo In co.emp
                allEmp.Add(emplo)
            Next
        Next

2：

    Dim min As Date = Nothing
        For Each c In Comps
            For Each em In c.emp
                If min = Nothing OrElse (em.DischargeDate > New Date(2018, 1, 1) AndAlso em.DischargeDate < min) Then
                    min = em.DischargeDate
                End If
            Next
        Next

我也尝试过

Dim xxx As List(Of List(Of employee)) = Comps.Select(Function(j) j.emp).ToList

但是通过这种方式，我得到了List(Of List(Of employee))而不是List(Of employee)

这些是课程

Public Class company
        Public name As String
        Public emp As List(Of employee)

    End Class

    Public Class employee
        Public name As String
        Public email As String
        Public DischargeDate As Date

    End Class

这里是收藏

        Private Comps As New List(Of company)

        Dim e As List(Of employee)

        Dim e1 As New employee With {.email = "aaa@aaa.aaa", .name = "nameEmp1", .DischargeDate = New Date(2019, 1, 12)}
        Dim e2 As New employee With {.email = "bbb@bbb.bbb", .name = "nameEmp2", .DischargeDate = New Date(2018, 8, 24)}
        Dim e3 As New employee With {.email = "ccc@ccc.ccc", .name = "nameEmp3", .DischargeDate = New Date(2017, 5, 12)}
        e = New List(Of employee) From {{e1}, {e2}, {e3}}
        Comps.Add(New company With {.name = "nameCom1", .emp = e})


        Dim e4 As New employee With {.email = "ddd@ddd.ddd", .name = "nameEmp4", .DischargeDate = New Date(2014, 3, 22)}
        Dim e5 As New employee With {.email = "eee@eee.eee", .name = "nameEmp5", .DischargeDate = New Date(2018, 4, 4)}
        Dim e6 As New employee With {.email = "fff@fff.fff", .name = "nameEmp6", .DischargeDate = New Date(2017, 3, 26)}
        e = New List(Of employee) From {{e4}, {e5}, {e6}}
        Comps.Add(New company With {.name = "nameCom2", .emp = e})



        Dim e7 As New employee With {.email = "ggg@ggg.ggg", .name = "nameEmp7", .DischargeDate = New Date(2019, 1, 8)}
        Dim e8 As New employee With {.email = "hhh@hhh.hhh", .name = "nameEmp8", .DischargeDate = New Date(2018, 6, 30)}
        Dim e9 As New employee With {.email = "iii@iii.iii", .name = "nameEmp9", .DischargeDate = New Date(2017, 2, 26)}
        e = New List(Of employee) From {{e7}, {e8}, {e9}}
        Comps.Add(New company With {.name = "nameCom3", .emp = e})

我将不胜感激任何建议或评论

Answer 1

第一个...

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    </div>
  <div class="card-body">
    <p class="card-text">Verticall center this image</p>
  </div>
</div>

第二个...

    Dim allEmp = (From co In Comps
                  From emplo In co.emp
                  Select emplo).ToList

    For Each emp As employee In allEmp
        Debug.Print(emp.name)
    Next

Answer 2

这两个都做：

Dim employees = Comps.SelectMany(Function(c) c.emp).ToList()
Dim oldestDischargedEmp As Employee = employees.
          Where(Function(e) e.DischargeDate > #2018-01-01#).
          OrderBy(Function(e) e.DischargeDate).
          First()

要记住的主要事情是，您可以使用第一部分的结果来帮助您找到第二部分的答案，从而避免重复工作。

还可以考虑删除.ToList()调用。仅凭IEnumerable<T>，您就能比想像的要频繁得多，这样做确实可以提高性能。

如何从另一个也是一个集合的项目中获取一个集合

2 个答案: