wpf - 错误 "Specified element is already the logical child of another element"？

Question

我有一个 TabControl，每个 Tab 可以包含相同的 UI，但具有不同的数据。在任何选项卡中，用户都可以单击一个按钮并弹出一个弹出窗口。这会为 ViewModel 设置一个 Style 属性，告诉它要为弹出 UI 使用什么样式。 Style 绑定(bind)到一个自定义的 DependecyProperty，该 DependecyProperty 附加到一个自定义的 PopupUserControl。我的问题是，当弹出窗口的第二个副本在另一个选项卡中打开时，我收到以下错误(无论应用了什么样式):

Specified element is already the logical child of another element. Disconnect it first.

按钮点击命令:

MyViewModel vm = ((Button)sender).DataContext as MyViewModel;
if (vm != null)
{
    Style popupStyle = (Style)Application.Current.FindResource("SomePopupStyle");
    vm.EditPanelStyle= popupStyle ;
}

这会触发 Style 上的 PropertyChange 事件

public Style EditPanelStyle
{
    get { return _editPanelStyle; }
    set
    {
        if (_editPanelStyle != value)
        {
            _editPanelStyle = value;
            OnPropertyChanged("EditPanelStyle");
        }
    }
}

这会触发 ViewModelBase 中的 OnPropertyChanged 事件

protected virtual void OnPropertyChanged(string propertyName)
{
    this.VerifyPropertyName(propertyName);

    PropertyChangedEventHandler handler = this.PropertyChanged;
    if (handler != null)
    {
        var e = new PropertyChangedEventArgs(propertyName);
        handler(this, e);
    }
}

错误发生在 handler(this, e); 行。在 ViewModelBase 中

编辑

TabItem 包含一个 Canvas 和一堆可以添加/删除/移动/等的面板。每个 Panel 都有自己的资源目录。在面板中，我可以很好地设置 PopupStyle，它可以毫无问题地应用。面板中使用的样式也在 PanelResourceDictionary 中定义。

失败者和成功者的主要区别在于样式位于不同的位置。

编辑#2
失败的样式 - LookupDialog 是自定义 WPF UserControl

<!-- Popup Style for LookupDialog -->
<Style x:Key="LookupDialogBaseStyle" TargetType="{x:Type localControls:DraggablePanel}" BasedOn="{StaticResource GenericPopupStyle}">
    <Setter Property="Canvas.Left" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualWidth, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.25}" />
    <Setter Property="Canvas.Top" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualHeight, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.3}" />
    <Setter Property="Width" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualWidth, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.5}" />
    <Setter Property="Height" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualHeight, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.4}" />

    <!--<Setter Property="localControls:PopupPanel.PopupEnterKeyCommand" Value="{Binding Path=SaveCommand}" />-->
    <Setter Property="localControls:PopupPanel.PopupEscapeKeyCommand" Value="{Binding Path=CancelCommand}" />

    <Setter Property="Header" Value="{Binding Path=Header}" />
    <Setter Property="localControls:PopupPanel.BackgroundOpacity" Value="0" />

    <Setter Property="Content">
        <Setter.Value>
            <localControls:LookupDialog 
                DataContext="{Binding}"
                BorderBrush="{StaticResource DarkColor}" />
        </Setter.Value>
    </Setter>
</Style>

<!-- Base Style for a Popup (DraggablePanel) -->
<Style x:Key="GenericPopupStyle" TargetType="{x:Type localControls:DraggablePanel}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type localControls:DraggablePanel}">
                <Border Height="{TemplateBinding Height}" Width="{TemplateBinding Width}">
                    <DockPanel>
                        <!-- Header -->
                        <Border 
                            DockPanel.Dock="Top"
                            MinHeight="20"
                            Background="{DynamicResource TabItem_BackgroundBrush_Unselected}"
                            BorderBrush="{StaticResource DarkColor}"
                            BorderThickness="1"
                            CornerRadius="5,5,0,0"
                            Padding="2,3,2,2"
                            SnapsToDevicePixels="True"
                            >

                            <ContentPresenter x:Name="PART_DraggablePanelHeader" ContentSource="Header" />
                        </Border>

                        <!-- Content -->
                        <Border Background="{StaticResource DefaultBackground}" 
                                BorderBrush="{StaticResource DarkColor}" 
                                BorderThickness="1,0,1,1"
                                SnapsToDevicePixels="True">
                            <ContentPresenter ContentSource="Content" />
                        </Border>
                    </DockPanel>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

有效的风格:

<!-- Example Popup Style for a Panel -->
<Style x:Key="AgentDesktop_NotesPanelPopupStyle" TargetType="{x:Type ContentControl}">
    <Setter Property="Canvas.Left" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualWidth, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.2}" />
    <Setter Property="Canvas.Top" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualHeight, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.32}" />
    <Setter Property="Width" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualWidth, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.6}" />
    <Setter Property="Height" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type localControls:PopupPanel}}, 
        Path=ActualHeight, Converter={StaticResource PercentToDoubleConverter}, ConverterParameter=.36}" />

    <Setter Property="localControls:PopupPanel.PopupEnterKeyCommand" Value="{Binding Path=SaveCommand}" />
    <Setter Property="localControls:PopupPanel.PopupEscapeKeyCommand" Value="{Binding Path=HidePopupCommand}" />

    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <!-- Control Template removed to make this easier to read, but it's created from standard WPF controls with nothing special -->
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Answer 1

我的问题是我正在设置 Content在我的风格中，Content不能有超过一个逻辑父级。我需要将其移至 Template反而。由于不想丢失基础样式，所以将内容设置在ContentTemplate HeaderedContentControl 的属性(我的代码中的 DraggablePanel)。

无论如何都要向戴维 +1 帮助我解决这个问题。