【发布时间】：2013-09-05 22:26:00
【问题描述】：
我相信这对某人来说将是一次扣篮...... 手指交叉
我的 ListView ItemsSource 绑定到我的 ViewModel 上名为 TileItems 的属性。
完美地填充列表视图。
在 ViewModel 中，您会看到 "existingTileItem.Transaction = e.Transaction" 。 . .单个列表视图项目完美更新。
在 ViewModel 中，您会看到“Me.TileItems.Remove(existingTileItem)”...该项目不会从视图中删除。它确实从 Me.TileItems 集合中成功删除，但视图中未显示更新。
附加信息：AbstractViewModel 实现了 INotificationPropertyChanged，我已经尝试在 TileItem 中覆盖 Equals 而不是覆盖它，并且周围都发生了相同的结果。我看过this 的回答和this 的回答，但他们没有回答我遇到的问题。
XAML：
<UserControl.DataContext>
<local:TransactionTileResultsViewControlViewModel />
</UserControl.DataContext>
<ListView Grid.Row="1" Name="tileItems" ItemsSource="{Binding TileItems, Mode=TwoWay}"
ItemTemplate="{StaticResource tileItemDataTemplate}" ScrollViewer.HorizontalScrollBarVisibility="Hidden"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
视图模型：
Public Class TransactionTileResultsViewControlViewModel
Inherits AbstractViewModel
Implements INavigationAware
Private _tileItems As TileItems
Public Property TileItems As TileItems
Get
Return Me._tileItems
End Get
Set(value As TileItems)
Me._tileItems = value
MyBase.RaisePropertyChanged("TileItems")
End Set
End Property
'....
#Region "TransactionUpdateReceived Methods"
Private Sub TransactionUpdateReceived_Handler(ByVal e As TransactionUpdatedEvent)
If e.Transaction IsNot Nothing Then
Dim existingTileItem As TileItem = Me.TileItems.Where(Function(t) t.Transaction.TransactionQueueID = e.Transaction.TransactionQueueID).FirstOrDefault()
If existingTileItem IsNot Nothing Then
If e.Transaction.Canceled Then
Me.TileItems.Remove(existingTileItem)
Else
If e.Transaction.ContainsFailedActivites() OrElse e.Transaction.ContainsCallbackActivities() Then
existingTileItem.Transaction = e.Transaction
Else
Me.TileItems.Remove(existingTileItem)
End If
End If
End If
End If
End Sub
#End Region
End Class
TileItems 模型：
Public Class TileItems
Inherits ObservableCollection(Of TileItem)
End Class
TileItem 模型：
Imports Microsoft.Practices.Prism.ViewModel
Public Class TileItem
Inherits NotificationObject
Private _created As Date
Public Property Created As Date
Get
Return _created
End Get
Set(value As Date)
_created = value
MyBase.RaisePropertyChanged("Created")
End Set
End Property
Private _category As String
Public Property Category As String
Get
Return _category
End Get
Set(value As String)
_category = value
MyBase.RaisePropertyChanged("Category")
End Set
End Property
Private _tileField1 As String
Public Property TileField1 As String
Get
Return _tileField1
End Get
Set(value As String)
_tileField1 = value
MyBase.RaisePropertyChanged("TileField1")
End Set
End Property
Private _tileField2 As String
Public Property TileField2 As String
Get
Return _tileField2
End Get
Set(value As String)
_tileField2 = value
MyBase.RaisePropertyChanged("TileField2")
End Set
End Property
Private _tileField3 As String
Public Property TileField3 As String
Get
Return _tileField3
End Get
Set(value As String)
_tileField3 = value
MyBase.RaisePropertyChanged("TileField3")
End Set
End Property
Private _transaction As Transaction
Public Property Transaction As Transaction
Get
Return _transaction
End Get
Set(value As Transaction)
_transaction = value
MyBase.RaisePropertyChanged("Transaction")
End Set
End Property
Public Overrides Function Equals(obj As Object) As Boolean
If TypeOf obj Is TileItem Then
Dim tileItem As TileItem = DirectCast(obj, TileItem)
If tileItem.Transaction IsNot Nothing AndAlso Me.Transaction IsNot Nothing Then
Return tileItem.Transaction.TransactionQueueID = Me.Transaction.TransactionQueueID
Else
Return False
End If
Else
Return False
End If
End Function
End Class
更新：
根据@ReedCopsey 的回答，这是我为使其正常工作而进行的更新。
我现在将 Me.TileItems.Remove(existingTileItem) 更新为这个
Me.View.Dispatcher.Invoke(Sub()
Me.TileItems.Remove(existingTileItem)
End Sub, DispatcherPriority.ApplicationIdle)
【问题讨论】：
-
为什么要为
TileItems创建自定义类？ -
在我不久前参加的 Billy Hollis 课程中，他说在使用泛型集合时要这样做......所以这只是习惯，在这种确切情况下可能不需要。我试过不这样做，也就是只使用 ObservableCollection(Of TileItem) 作为 TileItems 属性类型，结果相同。
-
总的来说，我实际上认为这是一种不好的做法 - 除非您添加额外的行为，否则无需创建额外的类来维护和测试。
-
@ReedCopsey ...嗯，好的。不确定这对我的问题有什么帮助，但感谢您的观察。记下:)
-
一般来说，除非您明确向其添加自定义逻辑，否则无需将集合包装到自定义类中。
标签： .net wpf mvvm viewmodel observablecollection