Question

使用lambda表达式时，有没有更好的方法在.NET中过滤泛型集合？注重可读性，但在使用lambda表达式或LINQ时，请避免使用不必要的代码并遵循最佳实践。

以下是一些过滤包含Pet类型对象的泛型集合的代码，我们希望使用PetType =＆＃34; Dog＆＃34;来获取所有对象的最小年龄。

Module Module1

    Public Class Pet
        Public Name As String
        Public Age As Integer
        Public PetType As String
    End Class

    Sub Main()
        ' Create an array of Pet objects. 
        Dim pets As New List(Of Pet) From {
                                            New Pet With {.Name = "Barley", .Age = 8, .PetType = "Dog"}, _
                                            New Pet With {.Name = "Boots", .Age = 4, .PetType = "Dog"}, _
                                            New Pet With {.Name = "Jacky", .Age = 1, .PetType = "Cat"}, _
                                            New Pet With {.Name = "Whiskers", .Age = 2, .PetType = "Dog"}
                                        }

        ' Find the youngest dog by passing a  
        ' lambda expression to the Min() method. 
        Dim min As Integer = pets.Where(Function(pet) pet.PetType = "Dog").Min(Function(pet) pet.Age)

        ' Display the result.
        Console.WriteLine("The youngest dog is age " & min)

        ' This code produces the following output: 
        ' 
        ' The youngest dog is age 2
        Console.ReadLine()
    End Sub

End Module

Answer 1

如果你想在VB中使这个更惯用（并且更简洁），你可以使用Aggregate子句如下：

Dim minAge = Aggregate p In pets Where p.PetType = "Dog" Into Min(p.Age)

Answer 2

效率不高，但略短，希望更具可读性：

Dim min As Integer =
  (From pet In pets Where pet.PetType = "Dog" Select pet.Age).Min

我只是将你的内联LINQ转换为查询样式。

使用lambda表达式时过滤泛型集合的最佳方法？

2 个答案: