题
示例-我有一个人班
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
末级
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
这仍然返回所有5个人，例如未应用到哪里，我在做什么错？
我还希望能够传递名称列表并仅返回那些名称
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
一般承认的答案
问题在于，Where不会更改集合。它返回新过滤的集合。
尝试这个：
Dim filteredPerson = people.Where(Function(fp) fp.Fname = "Bob")
（顺便说一句，我在这里看不到任何动态的东西……您在哪里使用动态LINQ？）
要添加多个Where子句，您需要这样的东西：
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
但是，我不认为这实际上是您想要做的。每个Where子句都将坚持Fname是指定的名称-而不是Bob 和 Dave！我认为您实际上想要可以更简单地表达的内容：
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
我们只想知道Fname是否在searchList ，这就是Contains所做的。
热门答案
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
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