blocks|key|4259291|text|在MVVM模式中，您不会在ViewModel中直接引用控件。在MVVM中，一切都是“绑定”的。您的inkCanvas将绑定到您的ViewModel中的属性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4259292|public+class+MyViewModel+:+INotifyPropertyChanged
{
++++private+readonly+StrokeCollection+_mystrokes;

++++public+MyViewModel+()
++++{
++++++++_mystrokes=+new+StrokeCollection();
++++++++(_mystrokesas+INotifyCollectionChanged).CollectionChanged+%2B=+delegate
++++++++{
++++++++++++//the+strokes+have+changed
++++++++};
++++}

++++public+event+PropertyChangedEventHandler+PropertyChanged;

++++public+StrokeCollection+MyStrokes
++++{
++++++++get
++++++++{
++++++++++++return+_mystrokes;
++++++++}
++++}

++++private+void+OnPropertyChanged(string+propertyName)
++++{
++++++++var+handler+=+PropertyChanged;

++++++++if+(handler+!=+null)
++++++++{
++++++++++++handler(this,+new+PropertyChangedEventArgs(propertyName));
++++++++}
++++}
}|code-block|syntax|javascript|4259293|和XAML：|4259294|<InkCanvas+Strokes="{Binding+MyStrokes}"/>|4259295|编辑:|offset|length|style|BOLD|4259296|也许您的解决方案是使用EventToCommand+:这允许将UI事件直接绑定到XAML中的ICommand+(并使用Args将引用传递给inkCancas)|4259297|<i:Interaction.Triggers>
++++<i:EventTrigger+EventName="Loaded">
++++++++<cmd:EventToCommand+Command="{Binding+Mode=OneWay,+Path=LoadedCommand}"
++++++++++++++++++++++++++++PassEventArgsToCommand="True"+/>
++++</i:EventTrigger>
</i:Interaction.Triggers>|4259298|entityMap^0|0|0|0|0|0|3|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@$M|11|N|12|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

In MVVM Pattern, you won't reference a Control directly in ViewModel. In MVVM, all is "binding". You inkCanvas will be binding to a property in your ViewModel.

<pre><code>public class MyViewModel : INotifyPropertyChanged
{
 private readonly StrokeCollection _mystrokes;

 public MyViewModel ()
 {
 _mystrokes= new StrokeCollection();
 (_mystrokesas INotifyCollectionChanged).CollectionChanged += delegate
 {
 //the strokes have changed
 };
 }

 public event PropertyChangedEventHandler PropertyChanged;

 public StrokeCollection MyStrokes
 {
 get
 {
 return _mystrokes;
 }
 }

 private void OnPropertyChanged(string propertyName)
 {
 var handler = PropertyChanged;

 if (handler != null)
 {
 handler(this, new PropertyChangedEventArgs(propertyName));
 }
 }
}
</code></pre>

And XAML:

<pre><code>&lt;InkCanvas Strokes="{Binding MyStrokes}"/&gt;
</code></pre>

Edit :

Maybe the workaround for your case is to use EventToCommand : this allow tobind an UI event to an ICommand directly in XAML ( and use Args to pass a ref to the inkCancas)

<pre><code>&lt;i:Interaction.Triggers&gt;
 &lt;i:EventTrigger EventName="Loaded"&gt;
 &lt;cmd:EventToCommand Command="{Binding Mode=OneWay, Path=LoadedCommand}"
 PassEventArgsToCommand="True" /&gt;
 &lt;/i:EventTrigger&gt;
&lt;/i:Interaction.Triggers&gt;
</code></pre>

blocks|key|4411026|text|根据上面的注释，一种方法是扩展Canvas，并将对CanvasRender的引用保留在该类中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4411027|public+class+MyCanvas+:+Canvas
{
++++private+CanvasRender+_canvasRender;
++++private+ProjectData+_data;

++++public+ProjectData+Data
++++{
++++++++get+{+return+_data;+}+++++++
++++++++set
++++++++{
++++++++++++_data+=+value;
++++++++++++_canvasRender+=+new+CanvasRender(this,+_data);
++++++++}
++++}

++++public+MyCanvas()+:+base()
++++{
++++}
}|code-block|syntax|javascript|4411028|您可能还想让ProjectData成为一个依赖属性，以便它是可绑定的。|4411029|这允许您维护MVVM模式，因为现在您可以用XAML编写：|4411030|<local:MyCanvas+ProjectData="{Binding+ViewModel.ProjectData}"+/>|4411031|entityMap^0|F|6|P|C|0|0|6|B|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|11|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

Per the comments above, one way to do this is to extend <code>Canvas</code> and keep the reference to <code>CanvasRender</code> inside that class.

<pre><code>public class MyCanvas : Canvas
{
 private CanvasRender _canvasRender;
 private ProjectData _data;

 public ProjectData Data
 {
 get { return _data; } 
 set
 {
 _data = value;
 _canvasRender = new CanvasRender(this, _data);
 }
 }

 public MyCanvas() : base()
 {
 }
}
</code></pre>

You'd probably want to also make <code>ProjectData</code> a Dependency Property so that it's bindable.

This allows you to maintain the MVVM pattern, because now you can write in XAML:

<pre><code>&lt;local:MyCanvas ProjectData="{Binding ViewModel.ProjectData}" /&gt;
</code></pre>

blocks|key|286207|text|如果要使用EventToCommand方法(您在另一个答案中尝试过)，那么不要使用PassEventArgsToCommand属性，而是使用CommandParameter属性并将其绑定到画布。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|286208|<i:Interaction.Triggers>
++++<i:EventTrigger+EventName="Loaded">
++++++++<cmd:EventToCommand+Command="{Binding+Path=CanvasLoadedCommand}"
++++++++++++++++++++++++++++CommandParameter="{Binding+ElementName=inkCanvas}"+/>
++++</i:EventTrigger>
</i:Interaction.Triggers>|code-block|syntax|javascript|286209|然后在你的ViewModel中：|286210|public+class+ViewModel
{
++++private+Canvas+m_canvas;

++++public+RelayCommand<Canvas>+CanvasLoadedCommand+{+get;+private+set;+}

++++public+ViewModel()+
++++{+
++++++++CanvasLoadedCommand+=+new+RelayCommand<Canvas>(canvas+=>++
++++++++{+
++++++++++++m_canvas+=+canvas;
++++++++});+
++++}
}|286211|因此，一旦加载了画布，就应该在视图模型中保存对它的引用。|286212|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

If your going to use the EventToCommand approach (which you tried in another answer), then instead of using the PassEventArgsToCommand property use the CommandParameter property and bind it to your Canvas.

<pre><code>&lt;i:Interaction.Triggers&gt;
 &lt;i:EventTrigger EventName="Loaded"&gt;
 &lt;cmd:EventToCommand Command="{Binding Path=CanvasLoadedCommand}"
 CommandParameter="{Binding ElementName=inkCanvas}" /&gt;
 &lt;/i:EventTrigger&gt;
&lt;/i:Interaction.Triggers&gt;
</code></pre>

Then in your ViewModel:

<pre><code>public class ViewModel
{
 private Canvas m_canvas;

 public RelayCommand&lt;Canvas&gt; CanvasLoadedCommand { get; private set; }

 public ViewModel() 
 { 
 CanvasLoadedCommand = new RelayCommand&lt;Canvas&gt;(canvas =&gt; 
 { 
 m_canvas = canvas;
 }); 
 }
}
</code></pre>

So as soon as your canvas is loaded, you should then have a reference to it saved in your view model.

I'm using Galasoft's Light MVVM for my Siverlight project.

I have setup everything as instructed: the <code>ViewModel</code> is bound to <code>View</code>'s <code>DataContext</code>;

I have a canvas named <code>inkCanvas</code> in the <code>View</code>.

When the <code>ViewModel</code> gets the updated project data, I need to reference <code>inkCanvas</code> to create a <code>CanvasRender</code> instance <code>public CanvasRender(Canvas canvas, ProjectData pdata)</code>.

The problem is in MVVM, the <code>ViewModel</code> knows nothing about <code>View</code>, so how can I reference a control (<code>inkCanvas</code>) in <code>View</code>?

P.S. (Edited): The workaround I made is: when I pass the project data to the <code>ViewModel</code>, I also pass the <code>inkCanvas</code> from <code>View</code>'s code-behind. hmmm, now my code-behind is not clean.

How to Workaround Referencing View's Controls

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

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我在我的Siverlight项目中使用了Galasoft的Light MVVM。我已经按照指示设置好了一切：ViewModel绑定到了View的DataContext；我在View中有一个名为inkCanvas的画布。当ViewModel获得更新后的项目数据时，我需要引用inkCanvas来创建一个CanvasRend...

问如何解决引用视图控件的问题
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