自定义Generic.IEqualityComparer（Of T）-编译器错误

Question

我正在尝试实现一个简单的IEqulityComparer以与LINQ集合一起使用。我编写了以下代码，出于讨论目的，这些代码简化为最简单的形式...

Public Structure bob
    Dim SiteID As Integer
    Dim fred As String
End Structure

Public Class insCompare
    Implements System.Collections.Generic.IEqualityComparer(Of bob)

    Public Function Equals(ByVal x As bob, ByVal y As bob) As Boolean
        Return IIf(x.SiteID = y.SiteID, True, False)

    End Function

    Public Function GetHashCode(ByVal x As bob) As Integer
        Return x.SiteID.GetHashCode()

    End Function

End Class

我的问题是两个函数都抛出编译器警告“函数'getHashCode'（或'Equals'）在基类'Object'中遮盖了可覆盖的方法。要覆盖基类方法，必须将该方法声明为'Overrides '。”

但是，如果我将它们声明为Overrides，则会出现错误“函数'GetHashCode'无法声明为Overrides，因为它没有覆盖基类中的函数。”！

我还在“ Implements”行上收到编译器错误，以至于我必须实现“ getHashCode”，但我认为这是第一个问题的结果。

我所有的研究都表明我应该没事-有人知道了吗？

Answer 1

这是对该问题的较晚答案，但根据文档，您可以使用以下内容。请注意包含了 Overloads 关键字。

Public Class MyModelComparer
    Implements Generic.IEqualityComparer(Of MyModel)

    Public Overloads Function Equals(x As MyModel, y As MyModel) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of MyModel).Equals
       ' do compare
    End Function

    Public Overloads Function GetHashCode(obj As MyModel) As Integer Implements System.Collections.Generic.IEqualityComparer(Of MyModel).GetHashCode
       ' do hashcode
    End Function

End Class

Answer 2

好吧，似乎可以通过重命名函数并将它们声明为“实现”来进行排序，尽管我在网上看到了数十个示例，但情况并非如此。不过，我现在收到一个运行时异常，我将单独发布该异常。

Public Class insCompare
    Implements System.Collections.Generic.IEqualityComparer(Of Object)

    Public Function Equals1(ByVal x As Object, ByVal y As Object) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of Object).Equals
        Return IIf(x.SiteID = y.SiteID, True, False)

    End Function

    Public Function GetHashCode1(ByVal x As Object) As Integer Implements System.Collections.Generic.IEqualityComparer(Of Object).GetHashCode
        Return x.SiteID.ToString.ToLower.GetHashCode()

    End Function

End Class