LINQ 中的量词操作
当序列中的部分或全部元素满足特定条件时，这些运算符将返回布尔值，即 True 或 False。
| 运算符 | 描述 | C# 查询表达式语法 | VB 查询表达式语法 |
|---|---|---|---|
| All | 如果序列中的所有元素都满足谓词条件，则返回值"True" | 不适用 | 聚合…在…进入All(…) |
| Any | 通过搜索序列来确定其中是否有元素满足指定条件 | 不适用 | 将…聚合到…Any() |
| Contains | 如果发现序列中存在特定元素，则返回"True"值；如果序列不包含该特定元素，则返回"false"值 | 不适用 | 不适用 |
All - All(Of TSource) 扩展方法示例
VB
Module Module1
Sub Main()
Dim barley As New Pet With {.Name = "Barley", .Age = 4}
Dim boots As New Pet With {.Name = "Boots", .Age = 1}
Dim whiskers As New Pet With {.Name = "Whiskers", .Age = 6}
Dim bluemoon As New Pet With {.Name = "Blue Moon", .Age = 9}
Dim daisy As New Pet With {.Name = "Daisy", .Age = 3}
Dim charlotte As New Person With {.Name = "Charlotte", .Pets = New Pet() {barley, boots}}
Dim arlene As New Person With {.Name = "Arlene", .Pets = New Pet() {whiskers}}
Dim rui As New Person With {.Name = "Rui", .Pets = New Pet() {bluemoon, daisy}}
Dim people As New System.Collections.Generic.List(Of Person)(New Person() {charlotte, arlene, rui})
Dim query = From pers In people
Where (Aggregate pt In pers.Pets Into All(pt.Age > 2))
Select pers.Name
For Each e In query
Console.WriteLine("Name = {0}", e)
Next
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
Class Person
Public Property Name As String
Public Property Pets As Pet()
End Class
Class Pet
Public Property Name As String
Public Property Age As Integer
End Class
End Module
当 VB 中的上述代码被编译并执行时，它会产生以下结果 −
Arlene Rui Press any key to continue.
Any 示例 - 扩展方法
VB
Module Module1
Sub Main()
Dim barley As New Pet With {.Name = "Barley", .Age = 4}
Dim boots As New Pet With {.Name = "Boots", .Age = 1}
Dim whiskers As New Pet With {.Name = "Whiskers", .Age = 6}
Dim bluemoon As New Pet With {.Name = "Blue Moon", .Age = 9}
Dim daisy As New Pet With {.Name = "Daisy", .Age = 3}
Dim charlotte As New Person With {.Name = "Charlotte", .Pets = New Pet() {barley, boots}}
Dim arlene As New Person With {.Name = "Arlene", .Pets = New Pet() {whiskers}}
Dim rui As New Person With {.Name = "Rui", .Pets = New Pet() {bluemoon, daisy}}
Dim people As New System.Collections.Generic.List(Of Person)(New Person() {charlotte, arlene, rui})
Dim query = From pers In people
Where (Aggregate pt In pers.Pets Into Any(pt.Age > 7))
Select pers.Name
For Each e In query
Console.WriteLine("Name = {0}", e)
Next
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
Class Person
Public Property Name As String
Public Property Pets As Pet()
End Class
Class Pet
Public Property Name As String
Public Property Age As Integer
End Class
End Module
当 VB 中的上述代码被编译并执行时，它会产生以下结果 −
Rui Press any key to continue.
linq_query_operators.html
