Прямокутник

Прямокутник

<Rectangle Fill="Blue" HorizontalAlignment="Left" Height="30" Margin="76,81,0,0" Stroke="Black" VerticalAlignment="Top" Width="100"/>    

Границя

<Border BorderThickness="4" CornerRadius="50,50,0,0" BorderBrush="Black" Background="#FF5A9AE0">

</Border>