vb.net - 比较两个自定义对象列表

Question

我有两个通用列表，我需要比较条目的任何添加或减去。这些列表属于包含用户连接详细信息的自定义类。

Dim ConnectedUsersOld As New List(Of ConnectedUser)
Dim ConnectedUsersNew As New List(Of ConnectedUser)

我想找到：

a) ConnectedUsersNew 列表中但不在 ConnectedUsersOld 列表中的任何 ConnectedUser。（本次会议的新用户）

b) ConnectedUsersOld 列表中的任何 ConnectedUser，但不在 ConnectedUsersNew 列表中。（自上次会话后离开的用户）

ConnectedUsers 对象有一个名为 username 的属性用于比较。

Answer 1

尝试这个：

Imports System.Linq
Imports System.Collections.Generic

Class Program
    Private Shared Sub Main(args As String())
        Dim ConnectedUsersOld As New List(Of ConnectedUser)() From { _
            New ConnectedUser() With { _
                Key .Id = 1 _
            }, _
            New ConnectedUser() With { _
                Key .Id = 2 _
            }, _
            New ConnectedUser() With { _
                Key .Id = 3 _
            } _
        }
        Dim ConnectedUsersNew As New List(Of ConnectedUser)() From { _
            New ConnectedUser() With { _
                Key .Id = 3 _
            }, _
            New ConnectedUser() With { _
                Key .Id = 4 _
            }, _
            New ConnectedUser() With { _
                Key .Id = 5 _
            } _
        }

        Dim comparer = New UserComparer()
        Dim newUsers = ConnectedUsersNew.Except(ConnectedUsersOld, comparer).ToList()
        Dim oldUsers = ConnectedUsersOld.Except(ConnectedUsersNew, comparer).ToList()
    End Sub

    Private Class ConnectedUser
        Public Property Id() As Integer
            Get
                Return m_Id
            End Get
            Set
                m_Id = Value
            End Set
        End Property
        Private m_Id As Integer
    End Class

    Private Class UserComparer
        Implements IEqualityComparer(Of ConnectedUser)

        Public Function Equals(x As ConnectedUser, y As ConnectedUser) As Boolean
            Return x.Id = y.Id
        End Function

        Public Function GetHashCode(obj As ConnectedUser) As Integer
            Return obj.Id
        End Function
    End Class
End Class