在通用列表中搜索对象 [英] Search for Object in Generic List

问题描述

 公共类Customer $ b是否可以通过Generic List中的某个属性搜索对象？ 
 $ b私人_id作为整数
 
私人_作为字符串
 
公共财产ID（）作为整数
获得
返回_id 
结束获取
 Set 
 _id = value 
 End Set 
 End Property 
 
公共属性Name（）As String 
 Get 
返回_name 
结束获取
 Set 
 _name = value 
结束Set 
 End Property 
 
 Public Sub New（id As Integer， name As String）
 _id = id 
 _name = name 
 End Sub 
 
 End Class 
  

然后加载并搜索

  
 
 list.Add（新客户（1，A）
 
 list.Add（新客户（2，B）
  

如何返回id = 1的客户对象？这是否与泛型中的谓词有关？

注意：我在VB.NET中做这个。

解决方案

是的，这与谓词有关：

你想要 Find（Of T）方法。你需要传入一个谓词（在这种情况下它是一种委托类型）。您如何构建该委托取决于您使用的是哪个版本的VB。如果你使用VB9，你可以使用lambda表达式。 （如果你使用的是VB9，你可能想首先使用LINQ而不是Find（Of T），请注意。）lambda表达式的形式如下所示：

  list.Find（function（c）c.ID = 1）
  

我不确定VB8是否支持与C＃2相同的匿名方法。如果你需要从VB8调用这个，我会看看我能想出什么。 （我更像是一个C＃人：）

Is it possible to search for an object by one of its properties in a Generic List?

Public Class Customer

    Private _id As Integer

    Private _name As String

    Public Property ID() As Integer
        Get
            Return _id
        End Get
        Set
            _id = value
        End Set
    End Property

    Public Property Name() As String
        Get
            Return _name
        End Get
        Set
            _name = value
        End Set
    End Property

    Public Sub New(id As Integer, name As String)
        _id = id
        _name = name
    End Sub

End Class

Then loading and searching

Dim list as new list(Of Customer)

list.Add(New Customer(1,"A")

list.Add(New Customer(2,"B")

How can I return customer object with id =1? Does this have to do with the "Predicate" in Generics?

Note: I am doing this in VB.NET.

解决方案

Yes, this has everything to do with predicates :)

You want the Find(Of T) method. You need to pass in a predicate (which is a type of delegate in this case). How you construct that delegate depends on which version of VB you're using. If you're using VB9, you could use a lambda expression. (If you're using VB9 you might want to use LINQ instead of Find(Of T) in the first place, mind you.) The lambda expression form would be something like:

list.Find(function(c) c.ID = 1)

I'm not sure if VB8 supports anonymous methods in the same way that C# 2 does though. If you need to call this from VB8, I'll see what I can come up with. (I'm more of a C# person really :)

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