与 MVVM 的命令绑定

Question

我的 WP7 应用程序允许用户回答其他人提出的问题。 问题是如何在问题下列出它们：目前我使用 MVVM 方法，它们都是 ObservableCollection 的一部分，与 LongListSelector 相关联。

<toolkit:LongListSelector ItemsSource="{Binding Items}" IsFlatList="True">

                            <toolkit:LongListSelector.DataContext>
                                <local:ResponsesViewModel/>
                            </toolkit:LongListSelector.DataContext>
                            <toolkit:LongListSelector.ItemTemplate>
                                <DataTemplate>
                                    <local:BoxRisposta />
                                </DataTemplate>
                            </toolkit:LongListSelector.ItemTemplate>                            
                         </toolkit:LongListSelector>

每个项目都绑定在一个名为 BoxRisposta 的自定义用户控件中，该控件包含用于显示用户名、用户回复时间的文本框，以及包含回复的 RichTextBox。

响应列表是此 ViewModel 类的一部分。

Public Class ResponsesViewModel
    Implements INotifyPropertyChanged

    Private _Items As ObservableCollection(Of Risposta)
    Public Property Items() As ObservableCollection(Of Risposta)
        Get
            Return _Items
        End Get
        Set(ByVal value As ObservableCollection(Of Risposta))
            _Items = value
        End Set
    End Property

    Public Sub New()
        Me.Items = New ObservableCollection(Of Risposta)()
        QuoteCommand = New ActionCommand(New Action(Of Object)(Sub(p)
                                                                   MessageBox.Show("quoted")
                                                               End Sub))
    End Sub

    Private _QuoteCommand As ICommand
    Public Property QuoteCommand As ICommand
        Get
            Return _QuoteCommand
        End Get
        Private Set(value As ICommand)
            _QuoteCommand = value
        End Set
    End Property


    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
    Private Sub NotifyPropertyChanged(ByVal propertyName As String)
        Dim handler As PropertyChangedEventHandler = PropertyChangedEvent
        If handler IsNot Nothing Then
            handler(Me, New PropertyChangedEventArgs(propertyName))
        End If
    End Sub
End Class

Public Class ActionCommand
    Implements ICommand
    Private execAction As Action(Of Object)
    Private canExecFunc As Func(Of Object, Boolean)

    Public Sub New(execAction As Action(Of Object))
        Me.execAction = execAction
    End Sub

    Public Sub New(execAction As Action(Of Object), canExecFunc As Func(Of Object, Boolean))
        Me.execAction = execAction
        Me.canExecFunc = canExecFunc
    End Sub

    Public Function CanExecute(parameter As Object) As Boolean Implements ICommand.CanExecute
        If canExecFunc IsNot Nothing Then
            Return canExecFunc.Invoke(parameter)
        Else
            Return True
        End If
    End Function

    Public Event CanExecuteChanged As System.EventHandler Implements ICommand.CanExecuteChanged

    Public Sub Execute(parameter As Object) Implements ICommand.Execute
        If execAction IsNot Nothing Then
            execAction.Invoke(parameter)
        End If
    End Sub

End Class

你看到我在里面添加了一个命令吗？我想在我的自定义用户控件中添加一个按钮，该按钮用作“引用按钮”，并告诉 ViewModel 类正在引用响应并传递该响应的内容。

我被困在这里，我不知道如何在这种特定情况下绑定命令，我有一个项目列表，而不仅仅是一个对象（互联网上的大多数示例都显示）

Answer 1

试试这个：

 <local:BoxRisposta  DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}"/>

现在您的用户控件使用与当前页面相同的数据上下文

Answer 2

我只需要传递父 LLS 的 DataContext：

<toolkit:LongListSelector.ItemTemplate>
                            <DataTemplate>
                                <local:BoxRisposta QuoteCommand="{Binding ElementName=ResponseList,
                               Path=DataContext.QuoteCommand}" DeleteCommand="{Binding ElementName=ResponseList,
                               Path=DataContext.DeleteCommand}"/>
                            </DataTemplate>
</toolkit:LongListSelector.ItemTemplate>