If you place a button on a Grid control, the button will be
placed in the center of Grid. If you are using a Canvas as your parent control
of Button, the Button will be placed in the left top corner of Canvas. 
You can use Margin property to position a button control. If
you are using a Canvas, you may also use Canvas.Left and Canvas.Top properties.
You may also use VerticalAlignment and HorizontalAlignment
attributes to set vertical alignment, and horizontal alignment of a button. 
The code snippet in Listing 2 sets the position of the Button
control in the left top corner of the page. 
<Button x:Name="DrawCircleButton"
Height="40" Width="120" 
        Canvas.Left="10" Canvas.Top="10"
        Content="Draw
Circle"
        VerticalAlignment="Top" 
        HorizontalAlignment="Left">
</Button>