0

例 - 個人クラスがあります 

Public Class Person
Private _fname As String
Public Property Fname() As String
    Get
        Return _fname
    End Get
    Set(ByVal value As String)
        _fname = value
    End Set
End Property
Private _lname As String
Public Property Lname() As String
    Get
        Return _lname
    End Get
    Set(ByVal value As String)
        _lname = value
    End Set
End Property
Private _age As Integer
Public Property Age() As Integer
    Get
        Return _age
    End Get
    Set(ByVal value As Integer)
        _age = value
    End Set
End Property

クラス終了

  Dim people As New List(Of Person)
    people.Add(New Person With {.Fname = "Alice", .Lname = "Apples", .Age = 1})
    people.Add(New Person With {.Fname = "Bob", .Lname = "Banana", .Age = 2})
    people.Add(New Person With {.Fname = "Charlie", .Lname = "Cherry", .Age = 3})
    people.Add(New Person With {.Fname = "Dave", .Lname = "Durian", .Age = 4})
    people.Add(New Person With {.Fname = "Eric", .Lname = "EggPlant", .Age = 10})

    Dim filteredPerson = From person In people
    filteredPerson.Where(Function(fp) fp.Fname = "Bob")

    Dim finalList = filteredPerson.ToList
    For Each p In finalList
        Debug.Print("FNAME: " + p.Fname)
    Next

これでも、適用されていない場所のように、5 人全員が返されます。何が間違っていますか?

また、名前のリストを渡して、それらのみを返すことができるようにしたいと考えています

  Dim searchList As New List(Of String)
    searchList.Add("Bob")
    searchList.Add("Dave")

    Dim filteredPerson = From person In people
    For Each s In searchList
        Dim innerName As String = s
        filteredPerson.Where(Function(fp) fp.Fname = innerName)
    Next
    Dim finalList = filteredPerson.ToList
    For Each p In finalList
        Debug.Print("FNAME: " + p.Fname)
    Next
4

2 に答える 2

2

問題は、 Where がコレクションを変更しないことです。新しくフィルタリングされたコレクションを返します。

これを試して：

 Dim filteredPerson = people.Where(Function(fp) fp.Fname = "Bob")

（ちなみに、ここには動的なものは何もありません...どこで動的LINQを使用していますか？）

Where複数の句を追加するには、次のようなものが必要です。

Dim searchList As New List(Of String)
searchList.Add("Bob")
searchList.Add("Dave")

Dim filteredPerson As IEnumerable(Of String) = people
For Each s In searchList
    Dim innerName As String = s
    filteredPerson = filteredPerson.Where(Function(fp) fp.Fname = innerName)
Next
Dim finalList = filteredPerson.ToList
For Each p In finalList
    Debug.Print("FNAME: " + p.Fname)
Next

しかし、それが実際にあなたがやりたいことだとは思いません。各Where句は、それが指定された名前であると主張します。BobとDaveFnameの両方になることはありません。私はあなたが実際にもっと簡単に表現できる何かを望んでいると思います:

Dim searchList As New List(Of String)
searchList.Add("Bob")
searchList.Add("Dave")

Dim filteredPerson = people.Where(Function(fp) searchList.Contains(fp.Fname))
Dim finalList = filteredPerson.ToList
For Each p In finalList
    Debug.Print("FNAME: " + p.Fname)
Next

私たちが知りたいのFnameはsearchList、 が にあるかどうかだけですContains。

于 2009-09-10T16:47:39.577 に答える
0 
Dim people As New List(Of Person)
people.Add(New Person With {.Fname = "Alice", .Lname = "Apples", .Age = 1})
people.Add(New Person With {.Fname = "Bob", .Lname = "Banana", .Age = 2})
people.Add(New Person With {.Fname = "Charlie", .Lname = "Cherry", .Age = 3})
people.Add(New Person With {.Fname = "Dave", .Lname = "Durian", .Age = 4})
people.Add(New Person With {.Fname = "Eric", .Lname = "EggPlant", .Age = 10}) 

Dim searchList As New List(Of String)
searchList.Add("Bob")
searchList.Add("Dave")

dim filteredItems = from p in people _
join i in searchList on p.FName equals i _
select p

dim personFound as Person

for each personFound in filteredItems
    Console.WriteLine(personFound.Lname)
next
于 2009-09-10T17:28:08.450 に答える