本文整理汇总了VB.NET中System.Collections.ObjectModel.KeyedCollection<TKey,TItem>类的典型用法代码示例。如果您正苦于以下问题:VB.NET KeyedCollection<TKey,TItem>类的具体用法?VB.NET KeyedCollection<TKey,TItem>怎么用?VB.NET KeyedCollection<TKey,TItem>使用的例子?那么, 这里精选的类代码示例或许可以为您提供帮助。
在下文中一共展示了KeyedCollection<TKey,TItem>类的2个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的VB.NET代码示例。
示例1: SimpleOrder
' 导入命名空间
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
' This class represents a very simple keyed list of OrderItems,
' inheriting most of its behavior from the KeyedCollection and
' Collection classes. The immediate base class is the constructed
' type KeyedCollection(Of Integer, OrderItem). When you inherit
' from KeyedCollection, the second generic type argument is the
' type that you want to store in the collection -- in this case
' OrderItem. The first generic argument is the type that you want
' to use as a key. Its values must be calculated from OrderItem;
' in this case it is the Integer field PartNumber, so SimpleOrder
' inherits KeyedCollection(Of Integer, OrderItem).
'
Public Class SimpleOrder
Inherits KeyedCollection(Of Integer, OrderItem)
' This is the only method that absolutely must be overridden,
' because without it the KeyedCollection cannot extract the
' keys from the items. The input parameter type is the
' second generic type argument, in this case OrderItem, and
' the return value type is the first generic type argument,
' in this case Integer.
'
Protected Overrides Function GetKeyForItem( _
ByVal item As OrderItem) As Integer
' In this example, the key is the part number.
Return item.PartNumber
End Function
End Class
Public Class Demo
Public Shared Sub Main()
Dim weekly As New SimpleOrder()
' The Add method, inherited from Collection, takes OrderItem.
'
weekly.Add(New OrderItem(110072674, "Widget", 400, 45.17))
weekly.Add(New OrderItem(110072675, "Sprocket", 27, 5.3))
weekly.Add(New OrderItem(101030411, "Motor", 10, 237.5))
weekly.Add(New OrderItem(110072684, "Gear", 175, 5.17))
Display(weekly)
' The Contains method of KeyedCollection takes TKey.
'
Console.WriteLine(vbLf & "Contains(101030411): {0}", _
weekly.Contains(101030411))
' The default Item property of KeyedCollection takes the key
' type, Integer.
'
Console.WriteLine(vbLf & "weekly(101030411).Description: {0}", _
weekly(101030411).Description)
' The Remove method of KeyedCollection takes a key.
'
Console.WriteLine(vbLf & "Remove(101030411)")
weekly.Remove(101030411)
Display(weekly)
' The Insert method, inherited from Collection, takes an
' index and an OrderItem.
'
Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
weekly.Insert(2, New OrderItem(111033401, "Nut", 10, .5))
Display(weekly)
' The default Item property is overloaded. One overload comes
' from KeyedCollection(Of Integer, OrderItem); that overload
' is read-only, and takes Integer because it retrieves by key.
' The other overload comes from Collection(Of OrderItem), the
' base class of KeyedCollection(Of Integer, OrderItem); it
' retrieves by index, so it also takes an Integer. The compiler
' uses the most-derived overload, from KeyedCollection, so the
' only way to access SimpleOrder by index is to cast it to
' Collection(Of OrderItem). Otherwise the index is interpreted
' as a key, and KeyNotFoundException is thrown.
'
Dim coweekly As Collection(Of OrderItem) = weekly
Console.WriteLine(vbLf & "coweekly(2).Description: {0}", _
coweekly(2).Description)
Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
coweekly(2) = New OrderItem(127700026, "Crank", 27, 5.98)
Dim temp As OrderItem = coweekly(2)
' The IndexOf method, inherited from Collection(Of OrderItem),
' takes an OrderItem instead of a key.
'
Console.WriteLine(vbLf & "IndexOf(temp): {0}", _
weekly.IndexOf(temp))
' The inherited Remove method also takes an OrderItem.
'
Console.WriteLine(vbLf & "Remove(temp)")
weekly.Remove(temp)
Display(weekly)
Console.WriteLine(vbLf & "RemoveAt(0)")
weekly.RemoveAt(0)
Display(weekly)
End Sub
Private Shared Sub Display(ByVal order As SimpleOrder)
Console.WriteLine()
For Each item As OrderItem In order
Console.WriteLine(item)
Next item
End Sub
End Class
' This class represents a simple line item in an order. All the
' values are immutable except quantity.
'
Public Class OrderItem
Public ReadOnly PartNumber As Integer
Public ReadOnly Description As String
Public ReadOnly UnitPrice As Double
Private _quantity As Integer = 0
Public Sub New(ByVal partNumber As Integer, _
ByVal description As String, _
ByVal quantity As Integer, _
ByVal unitPrice As Double)
Me.PartNumber = partNumber
Me.Description = description
Me.Quantity = quantity
Me.UnitPrice = unitPrice
End Sub
Public Property Quantity() As Integer
Get
Return _quantity
End Get
Set
If value < 0 Then
Throw New ArgumentException("Quantity cannot be negative.")
End If
_quantity = value
End Set
End Property
Public Overrides Function ToString() As String
Return String.Format( _
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}", _
PartNumber, _quantity, Description, UnitPrice, _
UnitPrice * _quantity)
End Function
End Class
输出:
110072674 400 Widget at 45.17 = 18,068.00 110072675 27 Sprocket at 5.30 = 143.10 101030411 10 Motor at 237.50 = 2,375.00 110072684 175 Gear at 5.17 = 904.75 Contains(101030411): True weekly(101030411).Description: Motor Remove(101030411) 110072674 400 Widget at 45.17 = 18,068.00 110072675 27 Sprocket at 5.30 = 143.10 110072684 175 Gear at 5.17 = 904.75 Insert(2, New OrderItem(...)) 110072674 400 Widget at 45.17 = 18,068.00 110072675 27 Sprocket at 5.30 = 143.10 111033401 10 Nut at .50 = 5.00 110072684 175 Gear at 5.17 = 904.75 coweekly(2).Description: Nut coweekly(2) = New OrderItem(...) IndexOf(temp): 2 Remove(temp) 110072674 400 Widget at 45.17 = 18,068.00 110072675 27 Sprocket at 5.30 = 143.10 110072684 175 Gear at 5.17 = 904.75 RemoveAt(0) 110072675 27 Sprocket at 5.30 = 143.10 110072684 175 Gear at 5.17 = 904.75
示例2: SimpleOrder
' 导入命名空间
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
' This class derives from KeyedCollection and shows how to override
' the protected ClearItems, InsertItem, RemoveItem, and SetItem
' methods in order to change the behavior of the default Item
' property and the Add, Clear, Insert, and Remove methods. The
' class implements a Changed event, which is raised by all the
' protected methods.
'
' SimpleOrder is a collection of OrderItem objects, and its key
' is the PartNumber field of OrderItem. PartNumber is an Integer,
' so SimpleOrder inherits KeyedCollection(Of Integer, OrderItem).
' (Note that the key of OrderItem cannot be changed; if it could
' be changed, SimpleOrder would have to override ChangeItemKey.)
'
Public Class SimpleOrder
Inherits KeyedCollection(Of Integer, OrderItem)
Public Event Changed As EventHandler(Of SimpleOrderChangedEventArgs)
' This parameterless constructor calls the base class constructor
' that specifies a dictionary threshold of 0, so that the internal
' dictionary is created as soon as an item is added to the
' collection.
'
Public Sub New()
MyBase.New(Nothing, 0)
End Sub
' This is the only method that absolutely must be overridden,
' because without it the KeyedCollection cannot extract the
' keys from the items.
'
Protected Overrides Function GetKeyForItem( _
ByVal item As OrderItem) As Integer
' In this example, the key is the part number.
Return item.PartNumber
End Function
Protected Overrides Sub InsertItem( _
ByVal index As Integer, ByVal newItem As OrderItem)
MyBase.InsertItem(index, newItem)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Added, newItem, Nothing))
End Sub
Protected Overrides Sub SetItem(ByVal index As Integer, _
ByVal newItem As OrderItem)
Dim replaced As OrderItem = Items(index)
MyBase.SetItem(index, newItem)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Replaced, replaced, newItem))
End Sub
Protected Overrides Sub RemoveItem(ByVal index As Integer)
Dim removedItem As OrderItem = Items(index)
MyBase.RemoveItem(index)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Removed, removedItem, Nothing))
End Sub
Protected Overrides Sub ClearItems()
MyBase.ClearItems()
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Cleared, Nothing, Nothing))
End Sub
End Class
' Event argument for the Changed event.
'
Public Class SimpleOrderChangedEventArgs
Inherits EventArgs
Private _changedItem As OrderItem
Private _changeType As ChangeType
Private _replacedWith As OrderItem
Public ReadOnly Property ChangedItem As OrderItem
Get
Return _changedItem
End Get
End Property
Public ReadOnly Property ChangeType As ChangeType
Get
Return _changeType
End Get
End Property
Public ReadOnly Property ReplacedWith As OrderItem
Get
Return _replacedWith
End Get
End Property
Public Sub New(ByVal change As ChangeType, ByVal item As OrderItem, _
ByVal replacement As OrderItem)
_changeType = change
_changedItem = item
_replacedWith = replacement
End Sub
End Class
Public Enum ChangeType
Added
Removed
Replaced
Cleared
End Enum
Public Class Demo
Public Shared Sub Main()
Dim weekly As New SimpleOrder()
AddHandler weekly.Changed, AddressOf ChangedHandler
' The Add method, inherited from Collection, takes OrderItem.
'
weekly.Add(New OrderItem(110072674, "Widget", 400, 45.17))
weekly.Add(New OrderItem(110072675, "Sprocket", 27, 5.3))
weekly.Add(New OrderItem(101030411, "Motor", 10, 237.5))
weekly.Add(New OrderItem(110072684, "Gear", 175, 5.17))
Display(weekly)
' The Contains method of KeyedCollection takes TKey.
'
Console.WriteLine(vbLf & "Contains(101030411): {0}", _
weekly.Contains(101030411))
' The default Item property of KeyedCollection takes the key
' type, Integer. The property is read-only.
'
Console.WriteLine(vbLf & "weekly(101030411).Description: {0}", _
weekly(101030411).Description)
' The Remove method of KeyedCollection takes a key.
'
Console.WriteLine(vbLf & "Remove(101030411)")
weekly.Remove(101030411)
' The Insert method, inherited from Collection, takes an
' index and an OrderItem.
'
Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
weekly.Insert(2, New OrderItem(111033401, "Nut", 10, .5))
' The default Item property is overloaded. One overload comes
' from KeyedCollection(Of Integer, OrderItem); that overload
' is read-only, and takes Integer because it retrieves by key.
' The other overload comes from Collection(Of OrderItem), the
' base class of KeyedCollection(Of Integer, OrderItem); it
' retrieves by index, so it also takes an Integer. The compiler
' uses the most-derived overload, from KeyedCollection, so the
' only way to access SimpleOrder by index is to cast it to
' Collection(Of OrderItem). Otherwise the index is interpreted
' as a key, and KeyNotFoundException is thrown.
'
Dim coweekly As Collection(Of OrderItem) = weekly
Console.WriteLine(vbLf & "coweekly(2).Description: {0}", _
coweekly(2).Description)
Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
coweekly(2) = New OrderItem(127700026, "Crank", 27, 5.98)
Dim temp As OrderItem = coweekly(2)
' The IndexOf method, inherited from Collection(Of OrderItem),
' takes an OrderItem instead of a key.
'
Console.WriteLine(vbLf & "IndexOf(temp): {0}", _
weekly.IndexOf(temp))
' The inherited Remove method also takes an OrderItem.
'
Console.WriteLine(vbLf & "Remove(temp)")
weekly.Remove(temp)
Console.WriteLine(vbLf & "RemoveAt(0)")
weekly.RemoveAt(0)
' Increase the quantity for a line item.
Console.WriteLine(vbLf & "coweekly(1) = New OrderItem(...)")
coweekly(1) = New OrderItem(coweekly(1).PartNumber, _
coweekly(1).Description, coweekly(1).Quantity + 1000, _
coweekly(1).UnitPrice)
Display(weekly)
Console.WriteLine()
weekly.Clear()
End Sub
Private Shared Sub Display(ByVal order As SimpleOrder)
Console.WriteLine()
For Each item As OrderItem In order
Console.WriteLine(item)
Next item
End Sub
Private Shared Sub ChangedHandler(ByVal source As Object, _
ByVal e As SimpleOrderChangedEventArgs)
Dim item As OrderItem = e.ChangedItem
If e.ChangeType = ChangeType.Replaced Then
Dim replacement As OrderItem = e.ReplacedWith
Console.WriteLine("{0} (quantity {1}) was replaced " & _
"by {2}, (quantity {3}).", item.Description, _
item.Quantity, replacement.Description, replacement.Quantity)
ElseIf e.ChangeType = ChangeType.Cleared Then
Console.WriteLine("The order list was cleared.")
Else
Console.WriteLine("{0} (quantity {1}) was {2}.", _
item.Description, item.Quantity, e.ChangeType)
End If
End Sub
End Class
' This class represents a simple line item in an order. All the
' values are immutable except quantity.
'
Public Class OrderItem
Private _partNumber As Integer
Private _description As String
Private _unitPrice As Double
Private _quantity As Integer
Public ReadOnly Property PartNumber As Integer
Get
Return _partNumber
End Get
End Property
Public ReadOnly Property Description As String
Get
Return _description
End Get
End Property
Public ReadOnly Property UnitPrice As Double
Get
Return _unitPrice
End Get
End Property
Public ReadOnly Property Quantity() As Integer
Get
Return _quantity
End Get
End Property
Public Sub New(ByVal partNumber As Integer, _
ByVal description As String, _
ByVal quantity As Integer, _
ByVal unitPrice As Double)
_partNumber = partNumber
_description = description
_quantity = quantity
_unitPrice = unitPrice
End Sub
Public Overrides Function ToString() As String
Return String.Format( _
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}", _
PartNumber, _quantity, Description, UnitPrice, _
UnitPrice * _quantity)
End Function
End Class
输出:
Widget (quantity 400) was Added. Sprocket (quantity 27) was Added. Motor (quantity 10) was Added. Gear (quantity 175) was Added. 110072674 400 Widget at 45.17 = 18,068.00 110072675 27 Sprocket at 5.30 = 143.10 101030411 10 Motor at 237.50 = 2,375.00 110072684 175 Gear at 5.17 = 904.75 Contains(101030411): True weekly(101030411).Description: Motor Remove(101030411) Motor (quantity 10) was Removed. Insert(2, New OrderItem(...)) Nut (quantity 10) was Added. coweekly(2).Description: Nut coweekly(2) = New OrderItem(...) Nut (quantity 10) was replaced by Crank, (quantity 27). IndexOf(temp): 2 Remove(temp) Crank (quantity 27) was Removed. RemoveAt(0) Widget (quantity 400) was Removed. coweekly(1) = New OrderItem(...) Gear (quantity 175) was replaced by Gear, (quantity 1175). 110072675 27 Sprocket at 5.30 = 143.10 110072684 1175 Gear at 5.17 = 6,074.75 The order list was cleared.