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
然后像这样称呼它......
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中设置谓词委托函数来实现这一目标?
不建议使用LINQ或lambdas,因为这是关于.NET 2.0版的问题.
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
然后使您的MyClass类型实现新的IKeyed接口