ist there a way to get a change notification if an attached property changed?
A simple example is a Canvas
with a Rectangle
in it. The position of the Rectange
is set by using the DepenendyProperties Canvas.Top
and Canvas.Left
. I'm using an Adorner to move the Rectangle around by changing the Canvas.Top
and Canvas.Left
.
<Canvas Width="500" Height="500" >
<Rectangle Width="40" Height="40" Canvas.Left="10" Canvas.Top="20" />
</Canvas>
The next step is to create an Arrow between two Rectangles
. In order to keep track of the moving Rectangles
the Arrow must get a change notification whenever the position of a Rectangle
changes. This would be easy if I could just get a changed notification when the Attached Property Canvas.Top
changes.
Thanks for any help, Michael
Why don't you use a binding ? That's precisely what they're designed for...
If, for some reason, you can't use a binding, you can add a handler to be notified when the value of the property changes :
var topDescriptor = DependencyPropertyDescriptor.FromProperty(Canvas.TopProperty, typeof(Rectangle));
var leftDescriptor = DependencyPropertyDescriptor.FromProperty(Canvas.LeftProperty, typeof(Rectangle));
topDescriptor.AddValueChanged(rectangle, rectangle_PositionChanged);
leftDescriptor.AddValueChanged(rectangle, rectangle_PositionChanged);
...
private void rectangle_PositionChanged(object sender, EventArgs e)
{
...
}
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