Question

我正在将DataTables转换为通用列表，并且需要一种快速简便的方法来实现Find函数。看来我将不得不使用Predicate。经过进一步调查，我似乎仍然无法重新创建功能。我有这个谓词......

Private Function ByKey(ByVal Instance As MyClass) As Boolean
    Return Instance.Key = "I NEED THIS COMPARISON TO BE DYNAMIC!"
End Function

然后这样称呼它......

Dim Blah As MyClass = MyList.Find(AddressOf ByKey)

但我没有办法将一个关键变量传递给这个谓词进行比较，就像我以前用DataTable做的那样......

Dim MyRow as DataRow = MyTable.Rows.Find(KeyVariable)

如何在VB.NET中设置谓词委托功能来实现这一目标？

不建议使用LINQ或lambdas，因为这是关于.NET 2.0版的问题。

Answer 1

只需将谓词放在类实例中：

Public Class KeyMatcher
    Public Sub New(ByVal KeyToMatch As String)
       Me.KeyToMatch = KeyToMatch
    End Sub

    Private KeyToMatch As String

    Public Function Predicate(ByVal Instance As MyClass) As Boolean
       Return Instance.Key = KeyToMatch
    End Function
End Class

然后：

Dim Blah As MyClass = MyList.Find(AddressOf New KeyMatcher("testKey").Predicate)

我们甚至可以有点想象，并使这个通用：

Public Interface IKeyed(Of KeyType)
    Public Key As KeyType
End Interface

Public Class KeyMatcher(Of KeyType)
    Public Sub New(ByVal KeyToMatch As KeyType)
       Me.KeyToMatch = KeyToMatch
    End Sub

    Private KeyToMatch As KeyType

    Public Function Predicate(ByVal Instance As IKeyed(Of KeyType)) As Boolean
       Return Instance.Key = KeyToMatch
    End Function
End Class

然后让你的MyClass类型实现新的IKeyed接口

使用VB.NET的DataTable.Rows.Find的通用列表等价物？

1 个答案: