Equals Remove wrong assignment inside Equals

问题

I have following class which i am using to compare some objects it looks like it:

 Imports System.Collections.Generic

Public Class Part
    Implements IEqualityComparer(Of Part)

    Public _comparisonType As EqualsComparmission

    Public Sub New(ComparisonType As EqualsComparmission)
        Me._comparisonType = ComparisonType
    End Sub

    Public Sub New()
    End Sub

    Public Property PartName() As String
        Get
            Return m_PartName
        End Get
        Set(value As String)
            m_PartName = value
        End Set
    End Property
    Private m_PartName As String

    Public Property PartId() As Integer
        Get
            Return m_PartId
        End Get
        Set(value As Integer)
            m_PartId = value
        End Set
    End Property
    Private m_PartId As Integer

    Public Overrides Function ToString() As String
        Return "ID: " & PartId & "   Name: " & PartName
    End Function


    Public Function Equals1(x As Part, y As Part) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of Part).Equals
        If x Is Nothing AndAlso y Is Nothing Then Return True
        If x Is Nothing OrElse y Is Nothing Then Return False

        Select Case _comparisonType
            Case EqualsComparmission.PartId
                Return x.PartId = y.PartId
            Case EqualsComparmission.PartName
                Return String.Equals(x.PartName, y.PartName)
            Case EqualsComparmission.PartId_and_PartName
                Return x.PartId = y.PartId AndAlso String.Equals(x.PartName, y.PartName)
            Case Else
                Throw New NotSupportedException("Unknown comparison type for parts: " & _comparisonType.ToString())
        End Select
    End Function

    Public Function GetHashCode1(obj As Part) As Integer Implements System.Collections.Generic.IEqualityComparer(Of Part).GetHashCode
        Select Case _comparisonType
            Case EqualsComparmission.PartId
                Return obj.PartId
            Case EqualsComparmission.PartName
                Return If(obj.PartName Is Nothing, 0, obj.PartName.GetHashCode())
            Case EqualsComparmission.PartId_and_PartName
                Dim hash = 17

                hash = hash * 23 + obj.PartId
                hash = hash * 23 + If(obj.PartName Is Nothing, 0, obj.PartName.GetHashCode())
                Return hash
            Case Else
                Throw New NotSupportedException("Unknown comparison type for parts: " & _comparisonType.ToString())
        End Select
    End Function

    Public Overrides Function Equals(obj As Object) As Boolean
        If obj Is Nothing Then
            Return False
        End If
        Dim objAsPart As Part = TryCast(obj, Part)
        Dim result As Boolean = False
        Select Case _comparisonType
            Case EqualsComparmission.PartId
                result = Me.PartId.Equals(objAsPart.PartId)
            Case EqualsComparmission.PartName
                result = Me.PartName.Equals(objAsPart.PartName)
            Case EqualsComparmission.PartId_and_PartName
                result = Me.PartId.Equals(objAsPart.PartId) And Me.PartName.Equals(objAsPart.PartName)
            Case Else
                Throw New NotSupportedException("Unknown comparison type for parts: " & _comparisonType.ToString())
        End Select

        Return result
    End Function

End Class


Public Enum EqualsComparmission

    PartId
    PartName
    PartId_and_PartName

End Enum

I am able to compare correctly Compare e.g:

   Console.WriteLine("Was it found: " & parts.Contains(New Part() With { _
         .PartId = 1634, _
         .PartName = "shift lever" _
    }, New Part(EqualsComparmission.PartId_and_PartName)))

but i got problem with Remove, the method is always going to Equals first enum value PartId, no matter what i send to constructor, why is that?

 Dim deleted As Boolean = parts.Remove(New Part(EqualsComparmission.PartId_and_PartName) With { 
             .PartId = 11, _
             .PartName = "al7a" _
        })

回答1:

Assuming that parts is a List(Of Part), you can simplify your removal (and checking) by using linq:

'check it exists
Debug.WriteLine("Was it found: " & parts.Exists(Function(x) x.PartId = 1634 And x.PartName = "shift lever"))

'Remove by PartId and PartName
Dim deleted As Integer = parts.RemoveAll(Function(x) x.PartId = 1634 And x.PartName = "shift lever")
'or just by PartId
Dim deleted As Integer = parts.RemoveAll(Function(x) x.PartId = 1634)
'or just by PartName
Dim deleted As Integer = parts.RemoveAll(Function(x) x.PartName = "shift lever")

You can just specify if you want to delete parts where the PartId matches or the PartName matches or both. This way you can get rid of the Equals and Enums

来源：https://stackoverflow.com/questions/27842628/equals-remove-wrong-assignment-inside-equals