Declaring a Window in XAML

<!-- Window1.xaml -->
<window class="HelloApp.Window1" x="http://schemas.microsoft.com/winfx/xaml/2005" xmlns="http://schemas.microsoft.com/winfx/avalon/2005" text="Hello">

<button name="button" width="200" height="25" click="button_Click">Click Hello!>/button>

</window>