将两个 ViewModel 的属性相互绑定/关联

Question

我直接从一张图片开始，展示我拥有的结构，这样我就可以用图片来提问。

我有一个这样的ParentModel：

Public Class ParentModel
    public Property ModelValue_A As String
    Public Property ModelValue_B As String
End Class

我有一个ParentViewModel，它有两个ChildViewModel 类型的属性。

Public Class ParentViewModel
    Public Property Parent As ParentModel
    Public Property ChildViewModel_A As ChildViewModel
    Public Property ChildViewModel_B As ChildViewModel

    Sub New
        ChildViewModel_A = New ChildViewModel()
        ChildViewModel_B = New ChildViewModel()
    End Sub
End Class

我的ParentView是这样的：

<DataTemplate>
    <StackPanel Orientation="Horizontal">
        <ContentPresenter Content="{Binding ChildViewModel_A}"/>
        <ContentPresenter Content="{Binding ChildViewModel_B}"/>
    </StackPanel>
</DataTemplate>

我的ChildViewModel是这样的：

Public Class ChildViewModel
    Private _ChildValue As String

    Public Property ChildValue As String
        Get
            Return _ChildValue
        End Get
        Set
            _ChildValue = Value
            NotifyPropertyChanged(NameOf(ChildValue))
        End Set
End Class

我的ChildView是这样的：

<DataTemplate>
    <TextBox Text="{Binding ChildValue}" />
</DataTemplate>

我的NotifyPropertyChanged 方法：

Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

Protected Sub NotifyPropertyChanged(info As [String])
    RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
End Sub

当我启动应用程序时，我得到一个类似于上图的视图。在那里，我可以通过输入ChildView 的TextBox 来更改ChildValue。但是，我仍然没有每个ChildValue 与其对应的ParentViewModel 属性之间的连接/关系：ChildViewModel_A 和ChildViewModel_B。

我的问题是：如何通过更改ChildValue 的ChildViewModel_A 来更改ModelValue_A，并分别通过更改ChildViewModel_B 的ChildValue 来更改ModelValue_B？ p>

Answer 1

您可以在ParentViewModel 类中为ChildViewModel(s) 连接一个事件处理程序到PropertyChanged 事件，并在这个类中设置ParentModel 的属性：

Public Class ParentViewModel
    Public Property Parent As ParentModel
    Public Property ChildViewModel_A As ChildViewModel
    Public Property ChildViewModel_B As ChildViewModel

    Sub New()
        ChildViewModel_A = New ChildViewModel()
        ChildViewModel_B = New ChildViewModel()

        AddHandler ChildViewModel_A.PropertyChanged, AddressOf OnPropertyChangedA
        AddHandler ChildViewModel_B.PropertyChanged, AddressOf OnPropertyChangedB

    End Sub

    Private Sub OnPropertyChangedA(sender As Object, e As PropertyChangedEventArgs)
        Parent.ModelValue_A = ChildViewModel_A.ChildValue
    End Sub

    Private Sub OnPropertyChangedB(sender As Object, e As PropertyChangedEventArgs)
        Parent.ModelValue_B = ChildViewModel_B.ChildValue
    End Sub
End Class