A rectangle with curved corners
<Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="WpfApplication1" Height="352" Width="334" WindowStartupLocation="CenterScreen"> <StackPanel> <Rectangle RadiusX ="20" RadiusY ="50" Fill ="DarkBlue" Width ="150" Height ="50"/> </StackPanel> </Window>