MinWidth , Width, and MaxWidth are used to manage the range of widths that a window can have during its lifetime, and are configured as follows.
<window>
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
MinWidth="300" Width="400" MaxWidth="500"></window>
Window height is managed by MinHeight, Height, and MaxHeight, and are configured as follows.
<window>
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
MinHeight="300" Height="400" MaxHeight="500"></window>
The following code shows a window that automatically sizes to fit its content, both vertically and horizontally
<window>
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
SizeToContent="WidthAndHeight">
</window>
In your example you would set the following.
<window>
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
MinHeight="640" MinWidth="480"></window>