Question

我下了两节课：

班级部分：

Imports System.Collections.Generic

Public Class Part
    Implements IEqualityComparer(Of Part)

    Public Sub New()
    End Sub

    Public Property _comparisonType As EqualsComparmission

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

    Public Property PartName() As String
    Public Property PartId() As Integer

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

End Class

Class PartCollection：

Public Class PartsCollection
    Implements ICollection(Of Part)

    Public Property _comparisonType As EqualsComparmission
    Private myList As List(Of Part)

    Public Sub New()
        If myList Is Nothing Then
            myList = New List(Of Part)
        End If
    End Sub

    Public Sub New(ComparisonType As EqualsComparmission)
        If myList Is Nothing Then
            myList = New List(Of Part)
        End If
        Me._comparisonType = ComparisonType
    End Sub

    Public Sub Add(item As Part) Implements ICollection(Of Part).Add
        myList.Add(item)
    End Sub

    Public Sub Clear() Implements ICollection(Of Part).Clear
        myList.Clear()
    End Sub

    Public Sub CopyTo(array() As Part, arrayIndex As Integer) Implements ICollection(Of Part).CopyTo
    End Sub

    Public Function GetEnumerator() As IEnumerator(Of Part) Implements IEnumerable(Of Part).GetEnumerator
        Return New PartsEnumeration(myList)
    End Function

    Public ReadOnly Property Count As Integer Implements ICollection(Of Part).Count
        Get
            Return myList.Count
        End Get
    End Property

    Public ReadOnly Property IsReadOnly As Boolean Implements ICollection(Of Part).IsReadOnly
        Get
            Return False
        End Get
    End Property

    Public Function Remove(item As Part) As Boolean Implements ICollection(Of Part).Remove
        Return myList.Remove(item)
    End Function

    Public Function GetEnumerator1() As IEnumerator Implements IEnumerable.GetEnumerator
        Return New PartsEnumeration(myList)
    End Function

    Public Function Contains(item As Part) As Boolean Implements ICollection(Of Part).Contains
        Select Case _comparisonType
            Case EqualsComparmission.PartId
                Return myList.Exists(Function(x) x.PartId = item.PartId)
            Case EqualsComparmission.PartName
                Return myList.Exists(Function(x) x.PartName = item.PartName)
            Case EqualsComparmission.PartId_and_PartName
                Return myList.Exists(Function(x) x.PartId = item.PartId And x.PartName = item.PartName)
            Case Else
                Throw New NotSupportedException("Unknown comparison type for parts: " & _comparisonType.ToString())
        End Select
    End Function
End Class

我想使用Part类中的Equals1代替，因为代码现在正在使用PartsCollection中的Contains1。我想问你在这种情况下我要做什么？我当前的代码正在运行，但我想切换到我之前创建的Equals1。

这是测试代码：

Dim myParts As New PartsCollection

    Dim John As New Part With { _
         .PartName = "John", _
         .PartId = 1 _
    }

    Dim Silva As New Part With { _
       .PartName = "Silva", _
       .PartId = 2 _
  }

    Dim Jimmy As New Part With { _
       .PartName = "Jimmy", _
       .PartId = 3 _
  }

    Dim James As New Part With { _
      .PartName = "James", _
      .PartId = 4 _
 }

    myParts.Add(John)
    myParts.Add(Silva)
    myParts.Add(Jimmy)
    myParts.Add(James)

    Console.WriteLine("SEARCHING FOR CONCRETE PART IF EXIST")

    myParts._comparisonType = EqualsComparmission.PartId_and_PartName
    Dim p As Boolean = myParts.Contains(New Part() With { _
      .PartName = "James", _
      .PartId = 45 _
 })

Answer 1

在一个地方或另一个地方拥有功能的原因通常是基于需要或最有用的地方而不是写入时。当然，您可以将代码复制到您喜欢的位置。

当前状态的一个问题是你应该是一个定义为Property的方法参数。每次使用时都需要设置comparisonType，这样您就可以确定它设置为应该是什么。其次，由于它对比较操作至关重要，因此您应该查看正在使用的内容。

调用Equals / Contains或集合类上的任何其他内容并不排除在item类上使用该方法。要从集合类中使用它：

Public Overloads Function Contains(p As Part, 
          compare As EqualsComparmission) As Boolean

    Dim query = Items.Where(Function(f) p.Equals(f, compare)).ToList
    Return query.Count <> 0

End Function

用法：

If myParts.Contains(newP, EqualsComparmission.PartId_and_PartName) Then

比较功能存在于Part Item类中，该集合只是调用它。这也允许你这样做：

If part1.Equals(part2)

更重要的是要使用的比较模式作为参数传递，指定用于此比较的模式。使用的实际查询取决于您需要知道的内容。

消耗等于而不是包含

1 个答案: