从ListView的ItemContainer设置ContextMenu的DataContext？

Question

我正在使用mvvm模式，但是我很难弄清楚如何在ListView的ItemContainerStyle中设置ContextMenu的DataContext。

我也不明白为什么ListView.ContextMenu和ListView的GridView.ColumnHeaderContextMenu可以看到我的视图模型中的属性和命令，而ListView.ItemContainerStyle内部的ContextMenu却不能。

错误

System.Windows.Data Error: 40 : BindingExpression路径错误：'AddMenuItem'属性在'object''Currency' (HashCode=43406546)'上未找到。 BindingExpression:Path=AddMenuItem; DataItem='Currency' (HashCode=43406546); target element is 'ContextMenu' (Name=''); target property is 'ItemsSource' (type 'IEnumerable')

视图

<!-- Removed styles for clarity. -->
<UserControl>

<!-- Add ElementSpy to the UserControl’s rsources -->
<UserControl.Resources>
    <framework:ElementSpy x:Key="spy" />
</UserControl.Resources>

<ListView ItemsSource="{Binding Currency}">

    <ListView.ItemContainerStyle>
        <Style TargetType="ListViewItem">
            <Setter Property="ContextMenu">
                <Setter.Value>
                    <!-- 'AddMenuItem' property not found on 'object' 'Currency' -->
                    <!-- ContextMenu ItemsSource="{Binding AddMenuItem}" / -->

                    <!-- Use the ElementSpy resource -->
                    <ContextMenu ItemsSource="{Binding Source={StaticResource spy}, Path=Element.DataContext.AddMenuItem}" />
                </Setter.Value>
            </Setter>
        </Style>
    </ListView.ItemContainerStyle>

    <ListView.ContextMenu>
        <!-- Works -->
        <ContextMenu ItemsSource="{Binding EditMenuItem}" />
    </ListView.ContextMenu>

    <ListView.View>
        <GridView>
            <GridView.ColumnHeaderContextMenu>
                <!-- Works -->
                <ContextMenu ItemsSource="{Binding SortMenuItem}" />
            </GridView.ColumnHeaderContextMenu>

            <GridViewColumn Header="Code"
                            DisplayMemberBinding="{Binding Path=Code}" />

            <GridViewColumn Header="Description"
                            DisplayMemberBinding="{Binding Path=Description}" />

            <GridViewColumn Header="Exchange Rate"
                            DisplayMemberBinding="{Binding Path=ExchangeRate}" />
        </GridView>

    </ListView.View>

</ListView>
</UserControl>

代码后台

[Export(ViewNames.CurrencyMasterView, typeof(IMasterView))]
[PartCreationPolicy(CreationPolicy.Shared)]
public partial class CurrencyMasterView
    : UserControl, IMasterView
{
    public CurrencyMasterView()
    {
        InitializeComponent();
    }

    [Import]
    private MasterViewModel ViewModel
    {
        set
        {
            this.DataContext = value;
        }
    }
}

ViewModel

[Export(typeof(MasterViewModel))]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class MasterViewModel
    : ViewModelBase
{
    [ImportingConstructor]
    public MasterViewModel(IGeneralController generalController, IRegionManager regionManager)
    {
    }

    public ObservableCollection<Currency> Currency
    {
        get
        {
            return this.currency;
        }

        set
        {
            if (this.currency != value)
            {
                this.currency = value;
                this.RaisePropertyChanged(() => this.Currency);
            }
        }
    }

    public List<MenuItemMvvm> SortMenuItem
    {
        get
        {
            return this.CreateSortMenuItem();
        }
    }

    public List<MenuItemMvvm> EditMenuItem
    {
        get
        {
            return this.CreateEditMenuItem();
        }
    }

    public List<MenuItemMvvm> AddMenuItem
    {
        get
        {
            return this.CreateAddMenuItem();
        }
    }

    private List<MenuItemMvvm> CreateEditMenuItem()
    {
        var menu = new List<MenuItemMvvm>();

        menu.Add(new MenuItemMvvm("_Edit")
        {
            Command = this.EditCommand,
            Icon = new Image
            {
                Source = new BitmapImage(new Uri("pack://application:,,,/POS.Modules.Core;component/Resources/Images/16X16/Edit.png"))
            }
        });

        menu.Add(new MenuItemMvvm("_Duplicate")
        {
            Command = this.DuplicateCommand,
            Icon = new Image
            {
                Source = new BitmapImage(new Uri("pack://application:,,,/POS.Modules.Core;component/Resources/Images/16X16/Copy.png"))
            }
        });

        menu.Add(new MenuItemMvvm("_Delete")
        {
            Command = this.DeleteCommand,
            Icon = new Image
            {
                Source = new BitmapImage(new Uri("pack://application:,,,/POS.Modules.Core;component/Resources/Images/16X16/Delete.png"))
            }
        });


        return menu;
    }

    // Other methods removed for clarity
}

- kevin

---

kevin: 参见 https://dev59.com/X3RB5IYBdhLWcg3wz6UK 和 https://dev59.com/a0zSa4cB1Zd3GeqPjh7E - 你可以通过 ContextMenu.PlacementTarget 进行绑定。 - Matt Hamilton

Answer 1

这个问题帮助我找到了答案。 WPF MenuItem.Command绑定到ElementName导致System.Windows.Data错误：4：无法找到引用的绑定源 我更新了源代码，以便其他遇到此问题的人可以参考。

为了快速参考，这是我所做的：

添加Josh Smith的ElementSpy类。使用ElementSpy启用ElementName绑定 将ElementSpy添加到UserControl的资源中。

<UserControl.Resources>
    <framework:ElementSpy x:Key="spy" />
</UserControl.Resources>

然后绑定到资源并使用Element属性绑定到您选择的DataContext和属性。

<ContextMenu ItemsSource="{Binding Source={StaticResource spy}, Path=Element.DataContext.AddMenuItem}" />

- H.B.

Answer 2

你需要在绑定中使用RelativeSource和PlacementTarget。我使用以下XAML代码添加一个上下文菜单来设置数据表格列的可见性。

  <DataGrid.ContextMenu>
                <ContextMenu>
                    <MenuItem Header="Spalten ein-/ausblenden">                           
                        <StackPanel>
                            <ItemsControl 
                            ItemsSource="{Binding RelativeSource={RelativeSource AncestorType=ContextMenu}, Path=PlacementTarget.Columns, Mode=OneWay}"
                            ItemTemplate="{StaticResource Visibility4DataGridColumns}"
                            ></ItemsControl>
                        </StackPanel>
                    </MenuItem>
                </ContextMenu>
            </DataGrid.ContextMenu>

- blindmeis