设置 DataContext 后重置依赖属性

Question

我在 WPF 中有一个 UserControl (AgreementDetails)，具有以下 DependencyProperty 和功能：

// UserControl AgreementDetails
    public int AgreementID
        {
            get { return Convert.ToInt32(GetValue(AgreementIDProperty)); }
            set { SetValue(AgreementIDProperty, value); }

        }

    public static readonly DependencyProperty AgreementIDProperty = DependencyProperty.Register("AgreementID", typeof(int), typeof(UC1001_AgreementDetails_View), new PropertyMetadata(null));

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        int id = AgreementID;

        if (id > 0)
        {
            GetData();
            SetBindingContext();
            this.Visibility = System.Windows.Visibility.Visible;
        }
        else
        {
            this.Visibility = System.Windows.Visibility.Collapsed;
        }
    }

    private void GetData()
    {
        ConsultantServiceClient client = new ConsultantServiceClient();
        _contract = new UC1001_ActiveAgreementContract();
        _contract = client.GetAgreementDetailsByAgreementID(AgreementID);
    }

    private void SetBindingContext()
    {
        this.DataContext = _contract;
    }

我使用此 UserControl 在另一个 UserControl（仪表板）中显示为工具提示，我在其中设置了 AgreementID 属性：

// Dashboard    
<Setter Property="DataGridCell.ToolTip">
      <Setter.Value>
             <my:UC1001_AgreementDetails_View Background="#FFF" Opacity="0.88" AgreementID="{Binding Months[9].AgreementID}"/>
      </Setter.Value>
</Setter>

在 AgreementDetails 中，我使用 AgreementID 从数据库中获取一些数据以显示在 UserControl 中。我第一次这样做，一切都很顺利。但是当我在 AgreementDetails 中将传入的 WCF DataContract 设置为 datacontext 时，AgreementID 属性重置为 0，因此第二次调用将不起作用，因为显然我没有与 AgreementID = 0 的协议。我检查并在 SetBindingContext 中重置了 AgreementID ();设置 DataContext 后的方法。

我怎样才能做到让 AgreementID 属性在我在 AgreementDetails 中设置新的 dataContext 后不会重置？？

如果需要，可以提供更多信息。

编辑：我现在有以下代码：

// Dependency properties
 public int AgreementID
 {
    get { return (int)GetValue(AgreementIDProperty); }
    set { SetValue(AgreementIDProperty, value); }
 }

 public UC1001_ActiveAgreementContract AgreementDetailsContract
 {
    get { return (UC1001_ActiveAgreementContract)GetValue(AgreementDetailsContractProperty); }
    set { SetValue(AgreementDetailsContractProperty, value); }

 }

    public static readonly DependencyProperty AgreementIDProperty = DependencyProperty.Register("AgreementID", typeof(int), typeof(UC1001_AgreementDetails_View), new PropertyMetadata(null));
    public static readonly DependencyProperty AgreementDetailsContractProperty = DependencyProperty.Register("AgreementDetailsContract", typeof(UC1001_ActiveAgreementContract), typeof(UC1001_AgreementDetails_View), new PropertyMetadata(null));

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        int id = AgreementID;

        if (id > 0)
        {
            GetData();
            SetBindingContext();
            this.Visibility = System.Windows.Visibility.Visible;
        }
        else
        {
            this.Visibility = System.Windows.Visibility.Collapsed;
        }
    }

    private void GetData()
    {
        ConsultantServiceClient client = new ConsultantServiceClient();
        AgreementDetailsContract = client.GetAgreementDetailsByAgreementID(AgreementID);
    }

    private void SetBindingContext()
    {
       this.DataContext = AgreementDetailsContract;
    }

我还有设置DataContext后AgreementID重置为0的问题。

另外，当我使用以下语句绑定时，我得到一个空标签：

<Label Content="{Binding RelativeSource={RelativeSource Self}, Path=AgreementDetailsContract.EndClientName}" />

已解决：

我删除了 SetDataBinding() 方法，因此 Binding 不会重置我的 DependencyProperty，并且对于我的标签的绑定，我使用了以下 Binding（而不是 RelativeSource Self）：

 <Label Content="{Binding ElementName=AgreementDetails, Path=AgreementDetailsContract.EndClientName}" Grid.Column="1" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="11,0,0,0" Name="_labelEindklant" VerticalAlignment="Top" />

ElementName=AgreementDetails 是我的用户控件的名称。奇怪的是，{RelativeSource Self} 没用...

Answer 1

当您在用户控件中设置数据上下文时，实际上您也在重置父控件（仪表板）中的数据上下文。这是相同的上下文。因此，您的协议 ID 不再在上下文中，因此会被重置。

编辑：其实我说的不是很好。您不会影响 Dashboard 中的数据上下文，但会影响该控件中声明的 AgreementId 绑定使用的数据上下文。绑定是在仪表板控件中声明的，但绑定实际上是在您正在重置的子控件的数据上下文中查找。

在这里查看我的类似问题： Setting DataContext within UserControl is affecting bindings in parent

编辑：这就是我的意思：

// UserControl AgreementDetails
public int AgreementID
{
    get { return Convert.ToInt32(GetValue(AgreementIDProperty)); }
    set { SetValue(AgreementIDProperty, value); }
}

//The new property to bind to instead of DataContext
public UC1001_ActiveAgreementContract Agreement
{
    get { return (UC1001_ActiveAgreementContract)GetValue(AgreementProperty); }
    private set { SetValue(AgreementProperty, value); }
}

public static readonly DependencyProperty AgreementIDProperty = DependencyProperty.Register("AgreementID", typeof(int), typeof(UC1001_AgreementDetails_View), new PropertyMetadata(null));

//should really be readonly dependency property
public static readonly DependencyProperty AgreementProperty = DependencyProperty.Register("Agreement", typeof(UC1001_ActiveAgreementContract), typeof(UC1001_AgreementDetails_View), new PropertyMetadata(null));**

private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
    int id = AgreementID;

    if (id > 0)
    {
        GetData();
        SetBindingContext();
        this.Visibility = System.Windows.Visibility.Visible;
    }
    else
    {
        this.Visibility = System.Windows.Visibility.Collapsed;
    }
}

private void GetData()
{
    ConsultantServiceClient client = new ConsultantServiceClient();
    _contract = new UC1001_ActiveAgreementContract();
    _contract = client.GetAgreementDetailsByAgreementID(AgreementID);
}

private void SetBindingContext()
{
    this.Agreement = _contract;
}

然后在您的 AgreementDetails.xaml 中，您可能有类似的内容：

<!-- Bound to property in DataContext -->
<TextBlock Text={Binding SomeContractProperty} />

需要更改为哪个绑定：

<!-- Bound to new property on UC1001_AgreementDetails_View (UserControl) -->
<TextBlock Text={Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UC1001_AgreementDetails_View}}, Path=Agreement.SomeContractProperty} />