have tested this, it worked, at least for me
var x1 = Canvas.GetLeft(e1);
var y1 = Canvas.GetTop(e1);
Rect r1 = new Rect(x1, y1, e1.ActualWidth, e1.ActualHeight);
var x2 = Canvas.GetLeft(e2);
var y2 = Canvas.GetTop(e2);
Rect r2 = new Rect(x2, y2, e2.ActualWidth, e2.ActualHeight);
if (r1.IntersectsWith(r2))
MessageBox.Show("Intersected!");
else
MessageBox.Show("Non-Intersected!");
ar ellipse1Geom = ellipse1.RenderedGeometry;
var ellipse2Geom = ellipse2.RenderedGeometry;
var detail = ellipse1Geom.FillContainsWithDetail(ellipse2Geom);
if(detail != IntersectionDetail.Empty)
{
// We have an intersection or one contained inside the other
}The Geometry.FillContainsWithDetail(Geometry) method is defined as
Returns a value that describes the intersection between the current geometry and the specified geometry.