Finally got the answer by adding path data
<Grid >
<Ellipse HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Stroke="Black" StrokeThickness="1" />
<Path Data="M10,0 L10,20 z" Stroke="Black" StrokeThickness="1" Stretch="Fill" />
<Path Data="M0,10 L20,10 z" Stroke="Black" StrokeThickness="1" Stretch="Fill" />
</Grid>
solved How to implement a circle button like below one in XAML