Question

我不明白为什么绑定适用于文本框但不适用于usercontrol。在下图中，您可以看到它应该如何工作。该服务可以绑定到黄色用户控件，此usercontrol包含我自己的类的属性。在我的情况下，此属性称为电子邮件。问题是，此电子邮件永远不会绑定到黄色用户控件。如果我用简单的“ TextBox ”控件替换usercontrol，它就可以正常工作。

请您告诉我如何获得Binding工作？

User control description of binding

Silvelright主页的代码隐藏

#Region "UserProfile"

    ''' <summary>
    ''' UserProfile Dependency Property
    ''' </summary>
    Public Shared ReadOnly UserProfileProperty As DependencyProperty = _
        DependencyProperty.Register("UserProfile", GetType(ServiceReference1.UserProfile), GetType(MainPage), _
            New Windows.PropertyMetadata(Nothing, _
                AddressOf OnUserProfileChanged))

    ''' <summary>
    ''' Gets or sets the UserProfile property.  This dependency property 
    ''' indicates ....
    ''' </summary>
    Public Property UserProfile() As ServiceReference1.UserProfile
        Get
            Return CType(GetValue(UserProfileProperty), ServiceReference1.UserProfile)
        End Get
        Set(ByVal value As ServiceReference1.UserProfile)
            SetValue(UserProfileProperty, value)
        End Set
    End Property

    ''' <summary>
    ''' Handles changes to the UserProfile property.
    ''' </summary>
    Private Overloads Shared Sub OnUserProfileChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
        Dim target As MainPage = CType(d, MainPage)
        Dim oldUserProfile As ServiceReference1.UserProfile = CType(e.OldValue, ServiceReference1.UserProfile)
        Dim newUserProfile As ServiceReference1.UserProfile = target.UserProfile
        target.OnUserProfileChanged(oldUserProfile, newUserProfile)
    End Sub

    ''' <summary>
    ''' Provides derived classes an opportunity to handle changes to the UserProfile property.
    ''' </summary>
    Protected Overridable Overloads Sub OnUserProfileChanged(ByVal oldUserProfile As ServiceReference1.UserProfile, ByVal newUserProfile As ServiceReference1.UserProfile)
        Me.DataContext = newUserProfile

    End Sub

#End Region

在跟踪属性时，“newUserProfile”项在代码隐藏中成功设置。

XAML

<UserControl x:Class="CH_App.ucUserEditor"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                          xmlns:my="clr-namespace:CH_App"

    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <TextBox Text="{Binding Path=Email}"/>
        <my:ucDbRow Title="Email" Value="{Binding Path=Email, Mode=TwoWay}" />
    </Grid>
</UserControl>

带有电子邮件绑定的Texbox可以像它应该的那样工作并显示电子邮件地址。 usercontrol不显示电子邮件地址。用户控件显示标题正确。

用户控件

<UserControl x:Class="CH_App.ucDbRow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:my="clr-namespace:CH_App"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
            DataContext="{Binding RelativeSource={RelativeSource Self}}"
    d:DesignHeight="300" d:DesignWidth="400">

    <StackPanel>
        <TextBlock x:Name="txtTitle" Text="{Binding Path=Title}" />
        <TextBox x:Name="txtValue" Text="{Binding Path=Value, Mode=TwoWay}"/>
    </StackPanel>
</UserControl>

usercontrol的代码隐藏

#Region "Title"

    ''' <summary>
    ''' Title Dependency Property
    ''' </summary>
    Public Shared ReadOnly TitleProperty As DependencyProperty = _
        DependencyProperty.Register("Title", GetType(String), GetType(ucDbRow), _
            New Windows.PropertyMetadata(""))

    ''' <summary>
    ''' Gets or sets the Title property.  This dependency property 
    ''' indicates ....
    ''' </summary>
    Public Property Title() As String
        Get
            Return CType(GetValue(TitleProperty), String)
        End Get
        Set(ByVal value As String)
            SetValue(TitleProperty, value)
        End Set
    End Property

#End Region



#Region "Value"

    ''' <summary>
    ''' Value Dependency Property
    ''' </summary>
    Public Shared ReadOnly ValueProperty As DependencyProperty = _
        DependencyProperty.Register("Value", GetType(String), GetType(ucDbRow), _
            New Windows.PropertyMetadata(""))

    ''' <summary>
    ''' Gets or sets the Value property.  This dependency property 
    ''' indicates ....
    ''' </summary>
    Public Property Value() As String
        Get
            Return CType(GetValue(ValueProperty), Object)
        End Get
        Set(ByVal value As String)
            SetValue(ValueProperty, value)
        End Set
    End Property

#End Region

Answer 1

编辑（插入）：

你正在使用Silverlight 4，我要么在Silverlight 5或WPF中进行测试，但两者都可能，但是WPF当然支持RelativeSourceBinding，但是你几乎没有。左边输出如果我是正确的，Visual Studio中的窗口会出现以下错误。

System.Windows.Data错误：BindingExpression路径错误：
  'VisualBasicSilverlightApplication1.ucDbRow'上找不到'电子邮件'属性   'VisualBasicSilverlightApplication1.ucDbRow'（HashCode = 72766）。
  BindingExpression：Path ='DataContext.Email'
  DataItem ='VisualBasicSilverlightApplication1.ucDbRow'（HashCode = 72766）;
  target元素是'VisualBasicSilverlightApplication1.ucDbRow'（Name =''）;
  target属性是'Value'（类型'System.String'）..

DataContext将通过usercontrol进行处理，除了usercontrol的toplevel / instance之外。
所以不要这样做：

<my:ucDbRow Title="Email" Value="{Binding Path=Email, Mode=TwoWay}" />

您需要在代码中更改的唯一内容是指向设置DataContext的元素，大多数情况下是LayoutRoot：（在ucUserEditor中）

<my:ucDbRow Title="Email" Value="{Binding ElementName=LayoutRoot, 
            Path=DataContext.Email, Mode=TwoWay}" />

上一个回答
您在CH_App.ucDbRow中使用此DataContext="{Binding RelativeSource={RelativeSource Self}}"覆盖绑定的datacontext。删除它并且Value有效，因为您已经将DataContext置于保留状态，但标题不再有效。

有一个解决方案：

将ucDbRow更改为：

<UserControl x:Class="CH_App.ucDbRow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">
    <Grid x:Name="LayoutRoot" Background="White" DataContext="{Binding}">
    <StackPanel>
      <TextBlock x:Name="txtTitle" Text="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path=Title}" Height="23"/>
      <TextBox x:Name="txtValue" Text="{Binding Path=Value, Mode=TwoWay}"/>
    </StackPanel>
  </Grid>
</UserControl>

注意：如果Bindings不起作用，请检查您的输出窗口，如果它在输出窗口中失败，则检查。

另外：

我建议不使用usercontrol作为控件。在我看来，usercontrols应该更多地用于表示单个上下文，而不是一半上下文中的一半上下文。开始将usercontrols更多地视为页面，并使用自定义控件和datatemplate进行详细工作。使用Grid构建更好的布局变得非常容易，这是（在我看来）WPF和Silverlight中最好的功能之一，不能被有序的用户控件打败。

如何设置datacontext和自定义usercontrol绑定

1 个答案: