[英]Binding property to dynamicaly created item of context menu
I'm trying to make Context Menu, which will have items depending on some data in code. 我正在尝试制作“上下文菜单”,该菜单中的项目取决于代码中的某些数据。 So, i have simple class, determining single item of menu
所以,我有简单的课堂,确定菜单的单个项目
class ContextMenuItem
{
public string ItemHeader {get; set;}
public Command ItemAction {get; set;
}
where Command is implementation of ICommand, and stores action, which will be fired once this item is selected. 其中Command是ICommand的实现,并存储操作,一旦选择此项目,将触发该操作。 Then i have class, serving as DataContext
然后我有课,作为DataContext
class SomeClass
{
public List<ContextMenuItem> ContextMenuItems {get; set;}
public string SomeProperty {get; set;}
public string SomeAnotherProperty {get; set;}
}
So, ContextMenuItems is list of actions I need in my context menu, which can be generated using different approaches. 因此,ContextMenuItems是我在上下文菜单中需要执行的操作的列表,可以使用不同的方法来生成。
And I'm creating dynamic context menu, using this approach . 我正在使用这种方法创建动态上下文菜单。
<ContextMenu ItemsSource="{Binding ContextMenuItems}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="{x:Type MenuItem}">
<Setter Property="Command" Value="{Binding ItemAction}"/>
<Setter Property="Header" Value="{Binding ItemHeader}"/>
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
So, i was suspecting this to work well. 所以,我怀疑这能很好地工作。 But, for some reason, binding works not the way I want it to.
但是,由于某种原因,绑定的工作方式并非我想要的那样。
<Setter Property="Command" Value="{Binding ItemAction}"/>
<Setter Property="Header" Value="{Binding ItemHeader}"/>
Somehow, data context for this lines is not ContextMenuItem
, but SomeClass
itself. 不知何故,此行的数据上下文不是
ContextMenuItem
,而是SomeClass
本身。 So, i can bind SomeProperty and SomeAnotherProperty here, but not ItemHeader or ItemAction. 因此,我可以在此处绑定SomeProperty和SomeAnotherProperty,但不能绑定ItemHeader或ItemAction。 And this ruins whole idea of dynamicaly created context menu.
这破坏了动态创建上下文菜单的整个想法。
So, how can i make this template recognize ContextMenuItem as its DataContext? 那么,如何使此模板将ContextMenuItem识别为其DataContext?
What i want to do can be accomplished using DataTemplate, but it gives us MenuItem inside MenuItem, and this is not good. 我想做的事可以使用DataTemplate完成,但它在MenuItem内给了我们MenuItem,这不好。
Update 更新资料
Full xaml code involving ListBox 涉及ListBox的完整XAML代码
<ListBox Margin="5, 5" Background="White" ItemsSource="{Binding SwitchAgents, UpdateSourceTrigger=PropertyChanged}" HorizontalContentAlignment="Stretch">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="3,1">
<Grid.ContextMenu>
<ContextMenu ItemsSource="{Binding ContextMenuItems}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Command" Value="{Binding ItemAction}"/>
<Setter Property="Header" Value="{Binding ItemHeader}"/>
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
</Grid.ContextMenu>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="7*"/>
</Grid.ColumnDefinitions>
<CheckBox IsChecked="{Binding Enabled, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="0,3"/>
<TextBlock Text="{Binding ObjectName}" Grid.Column="1" Margin="0,2"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
There is a sneaky trick to making this work. 进行这项工作有一个偷偷摸摸的技巧。 Normally I'd just use a RelativeSource in the binding to have it tunnel up to something with a DataContext.
通常,我只在绑定中使用RelativeSource使其通过DataContext隧道连接到某个对象。 The problem is that ContextMenu doesn't sit in the visual tree hierarchy, so RelativeSource has nothing to find.
问题在于ContextMenu不在可视树层次结构中,因此RelativeSource找不到任何内容。
The solution is outlined here: http://www.thomaslevesque.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited 这里概述了该解决方案: http : //www.thomaslevesque.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-herited
Copy/paste this class into your project somewhere: 将此类复制/粘贴到您的项目中的某个位置:
public class BindingProxy : Freezable
{
#region Overrides of Freezable
protected override Freezable CreateInstanceCore()
{
return new BindingProxy();
}
#endregion
public object Data
{
get { return (object)GetValue(DataProperty); }
set { SetValue(DataProperty, value); }
}
// Using a DependencyProperty as the backing store for Data. This enables animation, styling, binding, etc...
public static readonly DependencyProperty DataProperty =
DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
}
Then reference the namespace of the BindingProxy at the top of your Window/UserControl/whatever: 然后在Window / UserControl /任何位置的顶部引用BindingProxy的名称空间:
xmlns:local="clr-namespace:INSERTYOURNAMESPACEHERE"
Add the BindingProxy as a resource to your ListBox: 将BindingProxy作为资源添加到您的ListBox中:
<ListBox.Resources>
<local:BindingProxy x:Key="proxy" Data="{Binding}" />
</ListBox.Resources>
And finally set the Source of your ContextMenu ItemsSource binding to the proxy: 最后将您的ContextMenu ItemsSource绑定的Source设置为代理:
<ContextMenu ItemsSource="{Binding Data.ContextMenuItems, Source={StaticResource proxy}}" >
Refer below code. 请参考下面的代码。 it is working fine for me.
对我来说很好。
<Window x:Class="BindingListBox_Learning.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ListBox Margin="5, 5" Background="White" ItemsSource="{Binding SwitchAgents, UpdateSourceTrigger=PropertyChanged}" HorizontalContentAlignment="Stretch">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="3,1">
<Grid.ContextMenu>
<ContextMenu ItemsSource="{Binding ContextMenuItems}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Command" Value="{Binding ItemAction}"/>
<Setter Property="Header" Value="{Binding ItemHeader}"/>
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
</Grid.ContextMenu>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="7*"/>
</Grid.ColumnDefinitions>
<CheckBox IsChecked="{Binding Enabled, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="0,3"/>
<TextBlock Text="{Binding SomeProperty}" Grid.Column="1" Margin="0,2"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainViewModel();
}
}
class MainViewModel
{
public List<SomeClass> SwitchAgents { get; set; }
public MainViewModel()
{
SwitchAgents = new List<SomeClass>();
SomeClass obj = new SomeClass();
obj.SomeProperty = "Test";
List<ContextMenuItem> lst = new List<ContextMenuItem>();
lst.Add(new ContextMenuItem() { ItemHeader = "Hi", ItemAction = new BaseCommand(MenuClick) });
obj.ContextMenuItems = lst;
SwitchAgents.Add(obj);
}
void MenuClick(object obj)
{
// Do Menu Click Stuff
}
}
class ContextMenuItem
{
public string ItemHeader { get; set; }
public ICommand ItemAction { get; set; }
}
class SomeClass
{
public List<ContextMenuItem> ContextMenuItems { get; set; }
public string SomeProperty { get; set; }
public string SomeAnotherProperty { get; set; }
}
public class BaseCommand : ICommand
{
private Predicate<object> _canExecute;
private Action<object> _method;
public event EventHandler CanExecuteChanged;
public BaseCommand(Action<object> method)
: this(method, null)
{
}
public BaseCommand(Action<object> method, Predicate<object> canExecute)
{
_method = method;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
if (_canExecute == null)
{
return true;
}
return _canExecute(parameter);
}
public void Execute(object parameter)
{
_method.Invoke(parameter);
}
}
Instead of BaseCommand you use RelayCommand from MVVMLight OR DelegateCommand from PRISM. 可以使用MVVMLight中的RelayCommand或PRISM中的DelegateCommand代替BaseCommand。
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