在VB.NET中查找List(Of String)中的重复项

Question

我有一个customersList(of String),我试图找到重复的客户.

If Not customers.Count = customers.Distinct.ToList.Count Then
     customers = customers.Except(customers.Distinct.ToList)
End If

但我得到以下异常:

InvalidCastException
Unable to cast object of type '<ExceptIterator>d__99`1[System.String]' to type

'System.Collections.Generic.List`1 [System.String]'.

这是在列表中查找重复项的正确方法吗？

Answer 1

customers = customers.GroupBy(Function(m) m) _
                 .Where(Function(g) g.Count() > 1) _
                 .Select(Function(g) g.Key).ToList

Answer 2

VB版本:

Dim duplicates = listOfItems.GroupBy(Function(i) i)_
                            .Where(Function(g) g.Count() > 1)_
                            .[Select](Function(g) g.Key)

C#:

var duplicates = customers.GroupBy(x => x)
                          .Where(g => g.Count() > 1)
                          .Select(g => g.Key);