Question

我已经搜索了一个星期以找到答案，但我不能。

由于某些原因，我必须实施Windows.Data.Binding我的自我。所以我创建了一个类，并在其中放置一个私有的Binding对象：

Public Class Binding
Inherits MarkupExtension
Private _Binding As New Windows.Data.Binding

#Region "Properties"

Public Property ElementName() As String
    Get
        Return _Binding.ElementName
    End Get
    Set(value As String)
        _Binding.ElementName = value
    End Set
End Property

Public Property Mode() As BindingMode
    Get
        Return _Binding.Mode
    End Get
    Set(value As BindingMode)
        _Binding.Mode = value
    End Set
End Property

Public Property Source() As Object
    Get
        Return _Binding.Source
    End Get
    Set(value As Object)
        _Binding.Source = value
    End Set
End Property
#End Region
'*Other Properties of Windows.Data.Binding go inside region*

Public Overrides Function ProvideValue(serviceProvider As IServiceProvider) As Object
    If serviceProvider Is Nothing Then
        Return "Design Time"
    Else
        Dim k = _Binding.ProvideValue(serviceProvider)
        Return k
    End If
End Function
End Class

有效。我需要更改ProvideValue中的一些实现，为此，我需要找到绑定的来源。例如，我在XAML中有一个像这样的对象：

<TextBlock Text={local:Binding Path=UserID} />

好的，我的TextBlock绑定到{{1>} 什么...... ??

问题是绑定的来源是什么？和如何在UserID方法中访问？

感谢所有

Answer 1

这是一个如何使用服务提供商来获取目标的示例。绑定来源

Public Overrides Function ProvideValue(serviceProvider As IServiceProvider) As Object
    Dim service As IProvideValueTarget = DirectCast(serviceProvider.GetService(GetType(IProvideValueTarget)), IProvideValueTarget)
    Dim targetObject As DependencyObject = TryCast(service.TargetObject, DependencyObject)
    Dim targetProperty As DependencyProperty = TryCast(service.TargetProperty, DependencyProperty)

    'find source of the binding'
    Dim targetElement As FrameworkElement = TryCast(targetObject, FrameworkElement)
    If targetElement IsNot Nothing Then
        Dim sourceObject As Object = targetElement.DataContext

        'your logic here'
    End If
End Function

我建议只有在使用转换器和格式时无法实现相同的扩展时才创建自己的绑定扩展，并且如果有特定需要这样做的话。

请阅读此处以获取有关IServiceProvider http://msdn.microsoft.com/en-us/library/ee621338.aspx

的更多信息

WPF绑定源

1 个答案: