我尽可能地搜索了,而且我找不到这个具体问题的答案...... WPF绑定看起来很棒,但是我最终还是撞到了墙上通常情况下。
好的,我有一个单例类,它最终是我绑定的那个:
Imports System.ComponentModel
Imports System.Collections.ObjectModel
Public Class AmandaSeyfried
Implements INotifyPropertyChanged
Shared _config As New config
Public Event PropertyChanged(sender As Object, E As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
Protected Overridable Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
Private Shared _thisInstance As AmandaSeyfried
Protected Sub New()
' initialization goes here
End Sub
Public Shared Function GetSingleton() As AmandaSeyfried
' initialize object if it hasn't already been done
If _thisInstance Is Nothing Then
_thisInstance = New AmandaSeyfried
End If
' return the initialized instance
Return _thisInstance
End Function
Public Class CountryTranslation
Implements INotifyPropertyChanged
Private Property _englishCountryName As String = ""
Public Property EnglishCountryName As String
Get
Return _EnglishCountryName
End Get
Set(value As String)
If _englishCountryName <> value Then
_englishCountryName = value
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("EnglishCountryName"))
End If
End Set
End Property
Private Property _foreignCountryName As String = ""
Public Property ForeignCountryName As String
Get
Return _foreignCountryName
End Get
Set(value As String)
If _foreignCountryName <> value Then
_foreignCountryName = value
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("ForeignCountryName"))
End If
End Set
End Property
Public Event PropertyChanged(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
End Class
Private WithEvents _countryTranslations As New ObservableCollection(Of CountryTranslation)
Public Property CountryTranslations As ObservableCollection(Of CountryTranslation)
Get
If _config.GetKeyTextValue("countryTranslations") <> "" Then
Dim reader As New IO.StringReader(_config.GetKeyTextValue("countryTranslations"))
Dim Serializer As New Xml.Serialization.XmlSerializer(_countryTranslations.GetType)
_countryTranslations = Serializer.Deserialize(reader)
End If
Return _countryTranslations
End Get
Set(value As ObservableCollection(Of CountryTranslation))
_countryTranslations = value
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("CountryTranslations"))
End Set
End Property
Private Sub CountryTranslationCollectionChanged(sender As Object, e As Specialized.NotifyCollectionChangedEventArgs) Handles _countryTranslations.CollectionChanged
Dim newStringWriter As New IO.StringWriter
Dim NewSerializer As New Xml.Serialization.XmlSerializer(_countryTranslations.GetType)
NewSerializer.Serialize(newStringWriter, _countryTranslations)
_config.SaveKeyTextValue("countryTranslations", newStringWriter.ToString)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("CountryTranslations"))
End Sub
End Class
_config
是一个名不副实的助手类,用于存储和检索本地SqlCe实例中的数据。本质上,对象被序列化,存储在DB中,然后在需要的任何时候从DB中拉出并反序列化为对象。总而言之,它似乎运作得相当好。
我的问题是虽然我可以绑定到该对象,并且我可以通过CollectionChangedMethod处理程序监视何时在WPF DataGrid中添加行,但当CountryTranslation的两个属性中的任何一个发生更改时,我都不会收到任何通知
我的相关代码的其余部分是...... XAML ......显然更多,但我不相信绑定的XAML部分是责备,所以我将它修剪为相关的:
<toolkit:DataGrid Margin="12,12,12,12" ItemsSource="{Binding Path=KarenSmith.CountryTranslations, Mode=TwoWay}" AutoGenerateColumns="False" HorizontalAlignment="Stretch" Width="Auto" SelectionMode="Single">
<toolkit:DataGrid.Columns>
<toolkit:DataGridTextColumn Width="283" Binding="{Binding EnglishCountryName,Mode=TwoWay}" />
<toolkit:DataGridTextColumn Width="283" Binding="{Binding ForeignCountryName,Mode=TwoWay}" />
</toolkit:DataGrid.Columns>
</toolkit:DataGrid>
漂亮而简单的代码隐藏:
Public Class Preferences
Public Property KarenSmith As AmandaSeyfried = AmandaSeyfried.GetSingleton
Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
DataContext = Me
End Sub
Private Sub Close_Click(sender As System.Object, e As System.Windows.RoutedEventArgs)
Me.Close()
End Sub
End Class
如果我在CountryTranslation类的Getter和Setter上抛出一些断点,我可以监视它们何时被更改(通过数据网格,因此绑定工作),但尝试我可能无法弄清楚如何根据主类中的事件引发事件,以便随后更新数据存储区以显示更改。
答案 0 :(得分:2)
通常我会向CollectionChanged
添加一个ObservableCollection
事件,当事件被添加时会向其附加一个PropertyChanged
事件,并且该事件侦听器会侦听更改并将其作为需要的。
这是一个例子:(希望语法是正确的,因为我只是通过C#运行它到VB.Net转换器)
Public Sub New()
AddHandler MyCollection.CollectionChanged, AddressOf MyCollection_CollectionChanged
End Sub
Private Sub MyCollection_CollectionChanged(sender As Object, e As CollectionChangedEventArgs)
If e.NewItems IsNot Nothing Then
For Each item As MyItem In e.NewItems
AddHandler item.PropertyChanged, AddressOf MyItem_PropertyChanged
Next
End If
If e.OldItems IsNot Nothing Then
For Each item As MyItem In e.OldItems
RemoveHandler item.PropertyChanged, AddressOf MyItem_PropertyChanged
Next
End If
End Sub
Private Sub MyItem_PropertyChanged(sender As Object, e As PropertyChangedEventArgs)
If e.PropertyName = "Some Property" Then
DoWork()
End If
End Sub
C#版本如下所示:
public MyViewModel()
{
MyCollection.CollectionChanged += MyCollection_CollectionChanged;
}
void MyCollection_CollectionChanged(object sender, CollectionChangedEventArgs e)
{
if (e.NewItems != null)
foreach(MyItem item in e.NewItems)
item.PropertyChanged += MyItem_PropertyChanged;
if (e.OldItems != null)
foreach(MyItem item in e.OldItems)
item.PropertyChanged -= MyItem_PropertyChanged;
}
void MyItem_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "Some Property")
DoWork();
}