我在下面的代码中有一个类，除了我使用的IEqualityComparer中的equals和hash方法之外，我还想实现add，remove，item，{{1 }和count from list。所以我决定使用Inherits CollectionBase，IEnumerator和IEnumerable。
无论如何，例如当我使用Add它不会在Part类中使用Add方法时，或者当我为每个方法执行时，它不会去GetEnumerator下一步。有什么问题？
这是班级：
GetEnumerator (current,movenext,position)这是测试代码：
Imports System.Collections.Generic
Public Class Part
Inherits CollectionBase
Implements IEqualityComparer(Of Part), IEnumerator(Of Part), IEnumerable(Of Part)
Private _values As List(Of Part)
Private _currentIndex As Integer
Public Property _comparisonType As EqualsComparmission
Public Sub New(ComparisonType As EqualsComparmission)
Me._comparisonType = ComparisonType
End Sub
Public Sub New(values As List(Of Part))
_values = New List(Of Part)(values)
Reset()
End Sub
Public Sub New()
End Sub
Public Property PartName() As String
Public Property PartId() As Integer
Public Overrides Function ToString() As String
Return "ID: " & PartId & " Name: " & PartName
End Function
Public Sub Add(ByVal value As Part)
Me.List.Add(value)
End Sub
Public Sub Remove(ByVal Index As Integer)
If Index >= 0 And Index < Count Then
List.Remove(Index)
End If
End Sub
Public ReadOnly Property Item(ByVal Index As Integer) As Part
Get
Return CType(List.Item(Index), Part)
End Get
End Property
Public ReadOnly Property Current() As Part
Get
Return _values(_currentIndex)
End Get
End Property
Public ReadOnly Property Current1 As Object Implements IEnumerator.Current
Get
Return Current
End Get
End Property
Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
_currentIndex += 1
Return _currentIndex < _values.Count
End Function
Public Sub Reset() Implements IEnumerator.Reset
_currentIndex = -1
End Sub
#Region "IDisposable Support"
Private disposedValue As Boolean ' To detect redundant calls
' IDisposable
Protected Overridable Sub Dispose(disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
' TODO: dispose managed state (managed objects).
End If
' TODO: free unmanaged resources (unmanaged objects) and override Finalize() below.
' TODO: set large fields to null.
End If
Me.disposedValue = True
End Sub
' TODO: override Finalize() only if Dispose(ByVal disposing As Boolean) above has code to free unmanaged resources.
'Protected Overrides Sub Finalize()
' ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above.
' Dispose(False)
' MyBase.Finalize()
'End Sub
' This code added by Visual Basic to correctly implement the disposable pattern.
Public Sub Dispose() Implements IDisposable.Dispose
' Do not change this code. Put cleanup code in Dispose(disposing As Boolean) above.
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
#End Region
Public Function GetEnumerator1() As IEnumerator(Of Part) Implements IEnumerable(Of Part).GetEnumerator
Return CType(Me, IEnumerator)
End Function
Public ReadOnly Property Current2 As Part Implements IEnumerator(Of Part).Current
Get
Return Current
End Get
End Property
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
End Class
编辑：
为列表操作实现ICollection的PartsCollection：
Dim parts As New List(Of Part)()
parts.Add(New Part() With { _
.PartName = "ala", _
.PartId = 11 _
})
parts.Add(New Part() With { _
.PartName = "shift lever", _
.PartId = 1634 _
})
For Each aPart As Part In parts
Console.WriteLine(aPart)
Next
每个循环的PartsEnumeration：
Public Class PartsCollection
Implements ICollection(Of Part)
' Enumerators are positioned before the first element
' until the first MoveNext() call.
Dim position As Integer = -1
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 Add(item As Part) Implements ICollection(Of Part).Add
myList.Add(item)
End Sub
Public Sub Clear() Implements ICollection(Of Part).Clear
End Sub
Public Function Contains1(item As Part) As Boolean Implements ICollection(Of Part).Contains
Return myList.Contains(item)
End Function
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
End Get
End Property
Public ReadOnly Property IsReadOnly As Boolean Implements ICollection(Of Part).IsReadOnly
Get
End Get
End Property
Public Function Remove(item As Part) As Boolean Implements ICollection(Of Part).Remove
End Function
Public Function GetEnumerator1() As IEnumerator Implements IEnumerable.GetEnumerator
End Function
End Class
测试代码：
Public Class PartsEnumeration
Implements IEnumerator(Of Part)
Private mmyList As List(Of Part)
Dim position As Integer = -1
Public Sub New(ByVal myList As List(Of Part))
mmyList = myList
End Sub
Public ReadOnly Property Current As Part Implements IEnumerator(Of Part).Current
Get
Try
Return mmyList(position)
Catch ex As IndexOutOfRangeException
Throw New InvalidOperationException()
End Try
End Get
End Property
Public ReadOnly Property Current1 As Object Implements IEnumerator.Current
Get
Try
Return mmyList(position)
Catch ex As IndexOutOfRangeException
Throw New InvalidOperationException()
End Try
End Get
End Property
Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
If position < mmyList.Count - 1 Then
position += 1
Return True
End If
Return False
End Function
Public Sub Reset() Implements IEnumerator.Reset
position = -1
End Sub
#Region "IDisposable Support"
Private disposedValue As Boolean ' To detect redundant calls
' IDisposable
Protected Overridable Sub Dispose(disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
' TODO: dispose managed state (managed objects).
End If
' TODO: free unmanaged resources (unmanaged objects) and override Finalize() below.
' TODO: set large fields to null.
End If
Me.disposedValue = True
End Sub
' TODO: override Finalize() only if Dispose(ByVal disposing As Boolean) above has code to free unmanaged resources.
'Protected Overrides Sub Finalize()
' ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above.
' Dispose(False)
' MyBase.Finalize()
'End Sub
' This code added by Visual Basic to correctly implement the disposable pattern.
Public Sub Dispose() Implements IDisposable.Dispose
' Do not change this code. Put cleanup code in Dispose(disposing As Boolean) above.
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
#End Region
End Class
答案 0 :(得分：1)
您正在将两件相关但不相同的东西粘合在一起，并制作一个集合列表。
Dim parts As New List(Of Part)()
由于Part继承自CollectionBase，因此您正在创建一个Collections列表。应使用Collection类来实现管理列表/集合的方法，例如另一个问题中的Extension功能。它将为您管理列表。
Class Part
Property Name As String
Property ID As Integer
End Class
Class Parts
Private myList As New List(Of Part)
Public Sub Add(item As Part)
Public Function IndexOfPartName...
etc
Public Sub Remove(item As Part)
' some might just be wrappers:
Public Function Contains(p As Part) As Boolean
Return myList.Contains(Part)
End Function
End Class
使用这些代码的代码：
Friend myParts As New Parts
myParts.Add(New Part(...))
Dim p As Part = myParts.IndexOfPartName("screws")
一旦您计算出所需的功能及其使用方式，您可以将其更改为Inherit Collection<T>，这样您就可以For Each p As Part in Parts。但是在处理接口等之前，要努力获得可行的集合类。其中一些可能不需要，因为Collection<T>实现了所有这些。
您可能对以下内容感兴趣：Guidelines for Collections
-
要使您的零件集合类成为集合，而不是内部集合的包装器：
Imports System.ComponentModel
Class Parts
Inherits Collection(Of Part)
' ALREADY implemeted for you are:
' Contains, Count, Add, Clear, IndexOf, Insert, EQUALS
' Item, Items, Remove, RemoveAt and RemoveItem
因此，您需要做的就是覆盖那些做出与您想要的不同的方法，或者扩展IndexOfPartName等功能。
ICollection要求你从头开始编写一个集合，但是已经构建了轮子。