Question

我有一个带有一些数据的 ListView 和一个 ItemContainerStyle 来将 ContextMenu 绑定到每个项目（所以它只在点击时出现 ListView 中的项目我已经在 ListView.Resources 中定义了 ContextMenu 。如何正确触发 ContextMenuOpening 事件，然后在所述事件中访问 ContextMenuEventArgs 中的 ContextMenu ？

ListView.Resources>
            <ContextMenu x:Key="ItemContextMenu" FontFamily="Verdana" FontSize="14">
              //Rest of the ContextMenu
                <MenuItem Header="Custom Actions">

                </MenuItem>
            </ContextMenu>
</ListView.Resources>

现在，我试图在风格中设置事件设定器，

<ListView.ItemContainerStyle>
            <Style TargetType="{x:Type ListViewItem}">
                <Setter Property="ContextMenu" Value="{StaticResource ItemContextMenu}" />
                <EventSetter Event="ContextMenuOpening" Handler="ContextMenu_ContextMenuOpening" />
</ListView.ItemContainerStyle>

但是这会在C＃-Code中触发 NullPointerException （基本上是从https://docs.microsoft.com/en-us/dotnet/framework/wpf/advanced/how-to-handle-the-contextmenuopening-event复制的）

private void ContextMenu_ContextMenuOpening(object sender, ContextMenuEventArgs e)
    {
        FrameworkElement fe = e.Source as FrameworkElement;
        ContextMenu cm = fe.ContextMenu;

        List<MenuItem> customActions = new List<MenuItem>();


        customActions.Add(new MenuItem {Header = "First Thing"});
        customActions.Add(new MenuItem {Header = "Second Thing"});


        foreach (MenuItem mi in cm.Items) // here is the NullPointerException
        {
            if((String)mi.Header == "Custom Actions")
            {
                foreach(MenuItem cmi in customActions)
                {
                    mi.Items.Add(cmi);
                }
            }
        }
    }

如何在打开之前访问 ContextMenu 并修改它？

从ListViewItem打开ContextMenu时的ContextMenuOpening

0 个答案: