我有一个带有层次数据的树视图控件。它有一个带有四个选项的上下文菜单：Expand、Expand All、Collapse、Collapse All。我目前正在使用下列类别来显示/隐藏内容功能表项目：

Public Class clsTreeContextMenuVisibilityConverter
Implements IValueConverter

Public Function Convert(InValue As Object, InTargetType As Type, InParameter As Object, InCulture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert

    Dim node As TreeNode = Nothing

    If InValue Is Nothing Then
        Return Binding.DoNothing
    End If

    node = DirectCast(InValue, TreeNode)

    If InValue.[GetType]() <> GetType([Boolean]) Then
        If node.HasChildren AndAlso node.ParentNode Is Nothing Then 
            If node.IsExpanded Then
                Return Visibility.Collapsed
            End If              
            Return Visibility.Visible
        End If
    End If

    Return Binding.DoNothing

End Function

Public Function ConvertBack(InValue As Object, InTargetType As Type, InParameter As Object, InCulture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
    Throw New NotImplementedException()
End Function

结束类别
XAML文件：

<Style  x:Key="ExpandMenuItemStyle"
    TargetType="MenuItem">
    <Setter Property="FontWeight" Value="Bold" />
    <Setter Property="Visibility" Value="{Binding Converter={StaticResource VisConverter}}" />
</Style>

 <MenuItem Header="Expand" Style="{StaticResource ExpandMenuItemStyle}" />

VisConverter是转换器类的x：Key。我的问题是，如果展开了一个节点，我应该看到Collapse，反之亦然。同样，如果它是一个根父级节点，我应该看到Expand All。那么，我必须为所有四种情况编写单独的转换器吗？或者有智能的方法可以做到这一点吗？
如果需要更多信息，请告诉我。