自定义控件中的 WPF 绑定答案

【问题标题】：WPF Binding in Custom Control自定义控件中的 WPF 绑定
【发布时间】：2014-03-16 12:07:24
【问题描述】：

我在 WPF 中有一个 CustomControl。

[TemplatePart(Name = ControlSaveButtonName, Type = typeof(Button))]
[TemplatePart(Name = ControlCancelButtonName, Type = typeof(Button))]
[TemplatePart(Name = ControlPanelName, Type = typeof(Panel))]
public class BaseEditEntityControl : Control
{
    public const string ControlSaveButtonName = "PART_SaveButton";
    public const string ControlCancelButtonName = "PART_CancelButton";
    public const string ControlPanelName = "PART_Panel";

    static BaseEditEntityControl()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(BaseEditEntityControl), new FrameworkPropertyMetadata(typeof(BaseEditEntityControl)));
    }

    private Button _saveButtonControl;
    public Button SaveButtonControl
    {
        get { return _saveButtonControl; }
    }
    private Button _cancelButtonControl;
    public Button CancelButtonControl
    {
        get { return _cancelButtonControl; }
    }
    private Panel _panelControl;
    public Panel PanelControl
    {
        get { return _panelControl; }
    }

    public static readonly DependencyProperty EntityProperty = DependencyProperty.Register(
        "Entity", typeof(object), typeof(BaseEditEntityControl));
            //, new FrameworkPropertyMetadata
            //{
            //    BindsTwoWayByDefault = true,
            //    PropertyChangedCallback = BaseEntityPropertyChanged
            //});

    public object Entity
    {
        get { return GetValue(EntityProperty); }
        set { SetValue(EntityProperty, value); FillPropertyControls(); }
    }

    public BaseEditEntityControl()
    {
    }

    public override void OnApplyTemplate()
    {
         base.OnApplyTemplate();

        _saveButtonControl = GetTemplateChild(ControlSaveButtonName) as Button;
        _cancelButtonControl = GetTemplateChild(ControlCancelButtonName) as Button;
        _panelControl = GetTemplateChild(ControlPanelName) as Panel;

        if (_saveButtonControl != null) _saveButtonControl.Click += SaveButton_Click;
        if (_cancelButtonControl != null) _cancelButtonControl.Click += CancelButton_Click;
    }

    public void FillPropertyControls()
    { 
        //Some Code
    }

    //private static void BaseEntityPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    //{
    //    var baseEntityControl = d as BaseEditEntityControl;
    //    if (baseEntityControl == null) return;
    //
    //    baseEntityControl.Entity = e.NewValue as BaseEntity;
    //}
}

控制模板：

<Style x:Key="PassportEntityEditControlStyle" TargetType="{x:Type base:BaseEditEntityControl}">
    <Setter Property="IsTabStop" Value="False"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type base:BaseEditEntityControl}">
                <StackPanel x:Name="PART_Panel" Orientation="Vertical">
                    <TextBlock Text="{Binding Entity, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=base:BaseEditEntityControl}}"></TextBlock>
                </StackPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

控制使用：

<Style TargetType="propertyControls1:PersonPassportPropertyControl">
    <Setter Property="IsTabStop" Value="False"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="propertyControls1:PersonPassportPropertyControl">
                <Grid ScrollViewer.CanContentScroll="True">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"></ColumnDefinition>
                    </Grid.ColumnDefinitions>
                <base:BaseEditEntityControl x:Name="PART_Value" ScrollViewer.CanContentScroll="True"
                      Entity="{Binding PropertyBinding, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=propertyControls1:PersonPassportPropertyControl}}" 
                      Style="{StaticResource PassportEntityEditControlStyle}"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

PersonPassportPropertyControl 也是一个自定义控件。

问题：文本框已填充，但未调用“实体集”和 FillPropertyControls。如果取消注释 PropertyChangedCallback 则调用 BaseEntityPropertyChanged。

【问题讨论】：

您的观察是正确的，依赖属性既不调用setter，也不调用getter。这就是为什么您的注释代码是正确的。 setter/getter 中唯一有效的代码是 SetValue/GetValue。

标签： c# .net wpf binding custom-controls

【解决方案1】：

绑定不使用 get 和 set 访问器。

通过以下方式更改实体属性：

    //Entity Dependency Property
    public object Entity
    {
        get { return (object)GetValue(EntityProperty); }
        set { SetValue(EntityProperty, value); }
    }
    public static readonly DependencyProperty EntityProperty =
        DependencyProperty.Register("Entity", typeof(object), 
        typeof(BaseEditEntityControl),
        new UIPropertyMetadata(null),
        (d, e) => { FillPropertyControls(); });

【讨论】：

【解决方案2】：

这就是它的设计方式。文档中也明确提到 XAML 绕过属性包装器并直接调用 GetValue 和 SetValue。

来自MSDN：

其 XAML 处理器的当前 WPF 实现本质上是依赖属性感知。 WPF XAML 处理器使用属性系统加载二进制 XAML 时依赖属性的方法和处理作为依赖属性的属性。这有效绕过属性包装器。当您实现自定义依赖项时属性，您必须考虑这种行为并应避免将任何其他代码放在您的属性包装器中，而不是属性系统方法 GetValue 和 SetValue。

使用 PropertyChangeCallback 代替放置您想要在依赖属性更改时执行的代码。

【讨论】：