WPF Multiple CombinedGeometry - wpf

Question

I wish to bind a collection of viewmodels with X,Y,Radius properties to a CombinedGeometry of circles using Union. However it seems that CombinedGeometry only supports 2 Geometries.
Is there anyway around this limitation?
Example of what I'm aiming for
<Path Stroke="Black" StrokeThickness="1" Fill="#CCCCFF">
<Path.Data>
<CombinedGeometry GeometryCombineMode="Union" ItemsSource="{Binding Circles}">
<CombinedGeometry.Template>
<EllipseGeometry RadiusX="{Binding Radius}" RadiusY="{Binding Radius}" CenterX="{Binding X}" CenterY="{Binding Y}"/>
</CombinedGeometry.Template>
</CombinedGeometry>
</Path.Data>
</Path>
It is indeed possible to have CombinedGeometries within CombinedGeometry as seen below. However, I don't know how to set it up so that it is easily bindable.
<Path Stroke="Black" StrokeThickness="1" Fill="#CCCCFF">
<Path.Data>
<!-- Combines two geometries using the union combine mode. -->
<CombinedGeometry GeometryCombineMode="Union">
<CombinedGeometry.Geometry1>
<CombinedGeometry GeometryCombineMode="Union">
<CombinedGeometry.Geometry1>
<EllipseGeometry RadiusX="50" RadiusY="50" Center="200,200" />
</CombinedGeometry.Geometry1>
<CombinedGeometry.Geometry2>
<EllipseGeometry RadiusX="50" RadiusY="50" Center="125,200" />
</CombinedGeometry.Geometry2>
</CombinedGeometry>
</CombinedGeometry.Geometry1>
<CombinedGeometry.Geometry2>
<CombinedGeometry GeometryCombineMode="Union">
<CombinedGeometry.Geometry1>
<EllipseGeometry RadiusX="50" RadiusY="50" Center="100,100" />
</CombinedGeometry.Geometry1>
<CombinedGeometry.Geometry2>
<EllipseGeometry RadiusX="50" RadiusY="50" Center="150,120" />
</CombinedGeometry.Geometry2>
</CombinedGeometry>
</CombinedGeometry.Geometry2>
</CombinedGeometry>
</Path.Data>
</Path>

Answer 1

Are you looking for GeometryGroup ?
MSDN Code Sample :
<Path Stroke="Black" StrokeThickness="1" Fill="#CCCCFF">
<Path.Data>
<!-- Creates a composite shape from three geometries. -->
<GeometryGroup FillRule="EvenOdd">
<LineGeometry StartPoint="10,10" EndPoint="50,30" />
<EllipseGeometry Center="40,70" RadiusX="30" RadiusY="30" />
<RectangleGeometry Rect="30,55 100 30" />
</GeometryGroup>
</Path.Data>
</Path>

Answer 2

This code produces the same result as the second code by the OP:
<Path Stroke="Black" StrokeThickness="1" Fill="#CCCCFF">
<Path.Data>
<CombinedGeometry GeometryCombineMode="Union">
<CombinedGeometry.Geometry1>
<!-- any geometry here -->
<GeometryGroup/>
</CombinedGeometry.Geometry1>
<CombinedGeometry.Geometry2>
<GeometryGroup FillRule="Nonzero">
<EllipseGeometry RadiusX="50" RadiusY="50" Center="200,200" />
<EllipseGeometry RadiusX="50" RadiusY="50" Center="125,200" />
<EllipseGeometry RadiusX="50" RadiusY="50" Center="100,100" />
<EllipseGeometry RadiusX="50" RadiusY="50" Center="150,120" />
</GeometryGroup>
</CombinedGeometry.Geometry2>
</CombinedGeometry>
</Path.Data>
</Path>
And instead of all the <EllipseGeometry>, you can bind to a collection via Children="{Binding Circles}" in <GeometryGroup>.

Answer 3

I have kind of a similar problem and found a hepfull post here:
How to make the border trim the child elements?
You could also try to create a converter that receives the collection in that binding and builds up the combined geometries as desired.
I'll do exactly that now :)