.net - 从 VB.NET 中的 List(Of T) 中删除重复项

Question

我无法从列表中删除重复项。我做错了什么？

Dim Contacts As New List(Of Person)

...

' remove duplicates '
Contacts = Contacts.Distinct(New PersonEqualityComparer).ToList

我的平等比较器:

Public Class PersonEqualityComparer
    Implements IEqualityComparer(Of Person)
    Public Function Equals1(ByVal x As Person, ByVal y As Person) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of Person).Equals
        Return String.Equals(x.EmailAddress, y.EmailAddress, StringComparison.CurrentCultureIgnoreCase) AndAlso _
               String.Equals(x.GivenName, y.GivenName, StringComparison.CurrentCultureIgnoreCase) AndAlso _
               String.Equals(x.Surname, y.Surname, StringComparison.CurrentCultureIgnoreCase)
    End Function
    Public Function GetHashCode1(ByVal obj As Person) As Integer Implements System.Collections.Generic.IEqualityComparer(Of Person).GetHashCode
        Return obj.GetHashCode
    End Function
End Class

Answer 1

您需要实现 GetHashCode1 以便任意两个相等的对象具有相同的哈希码。

如果许多不相等的对象具有相同的哈希码，它的执行速度会慢得多，尤其是对于大型列表。换句话说，不要将其更改为 Return 0。

在您的情况下，最简单的实现是这样的:

Return StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.EmailAddress) _
   Xor StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.GivenName) _
   Xor StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.Surname)

如果您想要更强大的实现，请参阅 this answer .