另一个执行WPF事件到命令（有问题） [英] Another implementation of WPF Event to Command (with problems)

问题描述

我正在考虑将一个ICommand挂起到一个控件的事件的各种实现。因此，例如TextBox的GotFocus应该在View Model中调用GotFocusCommand。然后我有一个想法来实现我自己的版本（为了我自己的学习），它的工作正常，但我只能将一个事件链接到XAML中的一个命令。

这样可以正常工作：

 < Button 
 local：EventToCommand.Event =点击
 local：EventToCommand.Command ={Binding TestCommand}
 /> 
  

但这不是：

 < Button 
 local：EventToCommand.Event =点击
 local：EventToCommand.Command ={Binding ClickCommand}
 local：EventToCommand.Event = GotFocus
 local：EventToCommand.Command ={Binding GotFocusCommand}
 /> 
  

，因为它会导致重复的属性名称错误。

是否可以执行以下操作：

 < Button> 
< Some Xaml Element> 
< local：EventToCommand Event =点击Command ={Binding ClickCommand}/> 
< local：EventToCommand Event =GotFocusCommand ={Binding GotFocusCommand}/> 
< / Some Xaml Element> 
< / Button> 
  

将多个事件映射到命令？

解决方案

有几种方法可以使用附加属性或继承自Button，并添加自己的DependencyProperty，其中包含EventToCommand对象的列表，当您添加将该事件绑定到该命令。如果这看起来很混乱，我可以尝试一些例子。

C＃

  public class EventedButton：Button 
 {
 public static DependencyProperty EventCommandsProperty 
 = DependencyProperty.Register（EventCommands，typeof（EventToCommandCollection），typeof（EventedButton），new PropertyMetadata（null） ）; 
 
 
 public EventToCommandCollection EventCommands 
 {
 get 
 {
将this.GetValue（EventCommandsProperty）作为EventToCommandCollection返回; 
} 
 set 
 {
 this.SetValue（EventCommandsProperty，value）; 
} 
} 
 
 public EventedButton（）
 {
 this.EventCommands = new EventToCommandCollection（this）; 
} 
} 
  

Xaml：

 < local：EventedButton> 
< local：EventedButton.EventCommands> 
< local：EventToCommand /> 
< / local：EventedButton.EventCommands> 
< / local：EventedButton> 
  

在EventToCommandCollection内部，当将项目添加到集合中时，您将附加/分离到您想要的事件

更新：附加属性

以下是将集合作为附加属性执行的一些代码： p>

C＃

  public static DependencyProperty CommandsProperty = 
 DependencyProperty.RegisterAttached （
Commands，
 typeof（ICollection< EventToCommand>），
 typeof（DependencyObject），
 new PropertyMetadata（null，OnCommandsChanged））; 
 
 
 private static void OnCommandsChanged（DependencyObject d，DependencyPropertyChangedEventArgs e）
 {
 //附加/分离事件处理程序
} 
 
 public static void SetCommands（DependencyObject element，ICollection< EventToCommand> value）
 {
 element.SetValue（CommandsProperty，value）; 
} 
 
 public static ICollection< EventToCommand> GetCommands（DependencyObject element）
 {
 return（ICollection< EventToCommand>）element.GetValue（CommandsProperty）; 
} 
  

Xaml：

 < local：EventedButton> 
< local：EventToCommand.Commands> 
< local：EventToCommandCollection> 
< local：EventToCommand /> 
< / local：EventToCommandCollection> 
< / local：EventToCommand.Commands> 
< / local：EventedButton> 
  

I am looking at various implementations of hooking a ICommand up to a control's event. So for instance the GotFocus of a TextBox should call a GotFocusCommand in my View Model. I then got an idea to implement my own version (for my own learning) and it is working well, but I can only link one event to one command in the XAML.

( Basically I just use reflection to find the specified Event and then do a AddEventHandler that executes the command )

This works fine :

<Button 
  local:EventToCommand.Event="Click" 
  local:EventToCommand.Command="{Binding TestCommand}" 
  />  

But this does not :

<Button 
  local:EventToCommand.Event="Click" 
  local:EventToCommand.Command="{Binding ClickCommand}" 
  local:EventToCommand.Event="GotFocus" 
  local:EventToCommand.Command="{Binding GotFocusCommand}"
  />  

as you it leads to a duplicate attribute name error.

Would it be possible to do something like :

<Button>
  <Some Xaml Element>
    <local:EventToCommand Event="Click" Command="{Binding ClickCommand}" />
    <local:EventToCommand Event="GotFocus" Command="{Binding GotFocusCommand}" />
  </Some Xaml Element>
</Button>

to "map" multiple events to commands ?

解决方案

There are a couple of ways you could approach this, either using an Attached Property or inheriting from Button and adding your own DependencyProperty that contains a list of EventToCommand objects, and when you add to that collection you wire up the event to command. If this seems confusing, I can try to whip up some examples.

C#

    public class EventedButton : Button
{
    public static DependencyProperty EventCommandsProperty
        = DependencyProperty.Register("EventCommands", typeof(EventToCommandCollection), typeof(EventedButton), new PropertyMetadata(null));


    public EventToCommandCollection EventCommands
    {
        get
        {
            return this.GetValue(EventCommandsProperty) as EventToCommandCollection;
        }
        set
        {
            this.SetValue(EventCommandsProperty, value);
        }
    }

    public EventedButton()
    {
        this.EventCommands = new EventToCommandCollection(this);
    }
}

Xaml:

    <local:EventedButton>
        <local:EventedButton.EventCommands>
            <local:EventToCommand />
        </local:EventedButton.EventCommands>
    </local:EventedButton>

Inside of EventToCommandCollection, you would attach/detach to the Event you wanted when items are added to the collection.

UPDATE: Attached Property

Here is some code to do the collection as an attached property:

C#

        public static DependencyProperty CommandsProperty =
        DependencyProperty.RegisterAttached(
        "Commands",
        typeof(ICollection<EventToCommand>),
        typeof(DependencyObject),
        new PropertyMetadata(null, OnCommandsChanged));


    private static void OnCommandsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        // Attach/Detach event handlers
    }

    public static void SetCommands(DependencyObject element, ICollection<EventToCommand> value)
    {
        element.SetValue(CommandsProperty, value);
    }

    public static ICollection<EventToCommand> GetCommands(DependencyObject element)
    {
        return (ICollection<EventToCommand>)element.GetValue(CommandsProperty);
    }

Xaml:

    <local:EventedButton>
        <local:EventToCommand.Commands>
            <local:EventToCommandCollection>
                <local:EventToCommand/>
            </local:EventToCommandCollection>
        </local:EventToCommand.Commands>
    </local:EventedButton>

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