比較兩個包含類對象的通用列表

Question

如何比較cSystemCatalog類中的兩個通用列表（cSystem）？我想知道，如果列表中的一個包含更多或更少的類的對象，我也想比較_systemKey和_systemName

Public Class cSystemCatalog 
    Private _systems As List(Of cSystem) 

Public Class cSystem 
    Private _systemKey As Int32 
    Private _systemName As String 

Answer 1

If _systems1.Count > _systems2.Count Then 

Answer 2

If _systems1.Count = _systems2.Count AndAlso _ 
_systems1.All(Function(s1) _systems2.Any(Function(s2) _ 
s2._systemKey = s1._systemKey AndAlso s2._systemName = s1._systemName)) Then 

只要你可以使用LINQ：

Imports System.LINQ 

Answer 3

我通過實現IEquatable接口找到了解決方案。

Public Class cSystem Implements IEquatable(Of cSystem) 
    Private _systemKey As Int32 
    Private _systemName As String 

Public Overloads Function Equals(ByVal other As cSystem) As Boolean Implements IEquatable(Of cSystem).Equals 
    If other Is Nothing Then Return False 
    If _systemKey = other.SystemKey AndAlso _systemName = other.SystemName Then 
     Return True 
    Else 
     Return False 
    End If 
End Function 

Public Overrides Function Equals(ByVal obj As Object) As Boolean 
    If obj Is Nothing Then Return MyBase.Equals(obj) 

    If Not TypeOf obj Is cSystemThen 
     Throw New InvalidCastException("The 'obj' argument is not a cSystemobject.") 
    Else 
     Return Equals(DirectCast(obj, cSystem)) 
    End If 
End Function 

Public Shared Operator =(ByVal system1 As cSystem, ByVal system2 As cSystem) As Boolean 
    Return system1.Equals(system2) 
End Operator 

Public Shared Operator <>(ByVal system1 As cSystem, ByVal system2 As cSystem) As Boolean 
    Return Not system1.Equals(system2) 
End Operator 

然後我用的是包含在名單上的方法來比較兩種含cSystem類對象的泛型列表：

Dim valuesHasBeenChanged As Boolean 
If objSystemCatalog.Systems.Count = objOldSystemCatalog.Systems.Count Then 
    For Each system As cSystem In objSystemCatalog.Systems 
     If objOldSystemCatalog.Systems.Contains(system) = False Then 
      valuesHasBeenChanged = True 
     End If 
    Next 
ElseIf objSystemCatalog.Systems.Count > objOldSystemCatalog.Systems.Count Then 
    valuesHasBeenChanged = True 
ElseIf objSystemCatalog.Systems.Count < objOldSystemCatalog.Systems.Count Then 
    valuesHasBeenChanged = True 
End If