如何将命令绑定到祖先数据上下文？ WPF::MVVM

Question

我有一个 ContextMenu 和一个 button，在 TabControl 里面，我让按钮 Command 可以正常工作，但不知道如何绑定 Context menu items 命令。你能指出我做错了什么吗？

注意：CloseTabCommand和CloseAllTabsCommand这两个命令在将它们绑定到按钮时工作正常。

Xaml代码：

<TabControl ItemsSource="{Binding TabItems}">
                <TabControl.ItemTemplate>
                    <DataTemplate>
                        <DockPanel Width="120" ToolTip="{Binding HeaderText}">
                            <DockPanel.ContextMenu>
                                <ContextMenu>
                                    <MenuItem Header="Close Tab"
                                              Command="{Binding DataContext.CloseTabCommand, RelativeSource={RelativeSource AncestorType=TabControl}}"
                                              CommandParameter="{Binding ItemId}" />
                                    <MenuItem Header="Close All Tabs"
                                              Command="{Binding DataContext.CloseAllTabsCommand, RelativeSource={RelativeSource AncestorType=TabControl}}" />
                                </ContextMenu>
                            </DockPanel.ContextMenu>
                            <Button
                                Command="{Binding DataContext.CloseTabCommand, RelativeSource={RelativeSource AncestorType=TabControl}}"
                                CommandParameter="{Binding ItemId}"
                                Content="X"
                                Cursor="Hand"
                                DockPanel.Dock="Right"
                                Focusable="False"
                                FontFamily="Courier"
                                FontWeight="Bold"
                                FontSize="10"
                                VerticalContentAlignment="Center"
                                Width="15" Height="15" />
                            <ContentPresenter Content="{Binding HeaderText}" VerticalAlignment="Center" />
                        </DockPanel>
                    </DataTemplate>
                </TabControl.ItemTemplate>
                <TabControl.ItemContainerStyle>
                    <Style TargetType="TabItem">
                        <Setter Property="IsSelected" Value="{Binding IsSelected}" />
                    </Style>
                </TabControl.ItemContainerStyle>
            </TabControl>

视图模型代码：

private ObservableCollection<TabItemViewModel> _tabItems;
        public ObservableCollection<TabItemViewModel> TabItems {
            // if _tabItems is null initiate object.
            get { return _tabItems; }
            set { SetProperty(ref _tabItems, value); }
        }

编辑：

绑定到在 TabItemViewModel(TabControl ItemsSource) class 中声明的命令可以正常工作。但我想将当前 UserControl

的命令绑定到 ViewModel

Answer 1

您是否尝试过将 AncestorType 绑定到 Window 或 UserControl？

Command="{Binding CloseTabCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"

Answer 2

将DockPanel的Tag属性绑定到视图模型，然后将MenuItem的Command属性绑定到ContextMenu的PlacementTarget:

<DockPanel Width="120" ToolTip="{Binding HeaderText}"
           Tag="{Binding DataContext, RelativeSource={RelativeSource AncestorType=TabControl}}">
    <DockPanel.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Close Tab"
                      Command="{Binding PlacementTarget.Tag.CloseTabCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}"
                      CommandParameter="{Binding ItemId}" />
            ...

ContextMenu 驻留在它自己的可视树中，这就是为什么您不能使用 RelativeSource 绑定到父 TabControl，因为在可视树中没有父 TabControl。

如何将命令绑定到祖先数据上下文？ WPF::MVVM

How to bind command to ancestor datacontext? WPF :: MVVM

c#

wpf

contextmenu

itemtemplate

mvvm