如何設置datacontext和自定義usercontrol綁定

Question

我不明白爲什麼綁定工作的文本框，但不適用於usercontrol。 在下面的圖片中，您會看到它應該如何工作。該服務可以綁定到黃色的用戶控件，並且此用戶控件包含我自己的類的屬性。在我的情況下，這個屬性被稱爲電子郵件。問題是，這電子郵件永遠不會綁定到黃色的用戶控件。 如果我通過簡單的「TextBox」控件替換usercontrol，它就可以正常工作。

請你能指教我如何獲得綁定工作？跟蹤屬性時的Silvelright主頁

#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 

代碼隱藏的 「newUserProfile」 項目在代碼隱藏設置成功。

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> 

的Texbox與電子郵件的結合就像它應該和顯示的電子郵件地址。 usercontrol不顯示電子郵件地址。用戶控件顯示標題正確。

用戶控件

<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> 

用戶控件的代碼隱藏

#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

編輯（插入）：

您使用Silverlight 4中，我要麼在測試從中獲得Silverlight 5或WPF b或許，但
WPF肯定支持RelativeSourceBinding這種方式，但你幾乎是正確的。
如果我是正確的，Visual Studio中的輸出窗口會給你以下錯誤。

System.Windows.Data Error: BindingExpression path error:
'Email' property not found on 'VisualBasicSilverlightApplication1.ucDbRow'
'VisualBasicSilverlightApplication1.ucDbRow' (HashCode=72766).
BindingExpression: Path='DataContext.Email'
DataItem='VisualBasicSilverlightApplication1.ucDbRow' (HashCode=72766);
target element is 'VisualBasicSilverlightApplication1.ucDbRow' (Name='');
target property is 'Value' (type 'System.String')..

DataContext將落在usercontrol中，除了usercontrol的頂級/實例。
因此，而不是這樣做：

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

你將不得不在你的代碼改變的唯一事情是指向您設置的DataContext的元素，這是大多數時間LayoutRoot：
（在ucUserEditor）

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

以前的答案
要覆蓋本DataContext="{Binding RelativeSource={RelativeSource Self}}"在CH_App.ucDbRow綁定的DataContext的。刪除它，價值工作，因爲你已經得到你的underlaying DataContext回來，但標題不再工作。

有一個解決方案：

變化ucDbRow這樣：

<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：檢查您的輸出中的窗口，如果綁定不工作，如果它失敗了它在輸出窗口。

另外：

我建議不使用UserControl的作爲對照的。在我看來，用戶控件應該更多地用於表示個人情境，而不是一個半環境的另一半。開始將用戶控件更多地視爲頁面，並使用自定義控件和數據模板來進行詳細的工作。使用Grid（也是我認爲的）WPF和Silverlight中最好的功能之一，不能被有序的用戶控件擊敗，因此構建更好的佈局變得非常容易。