Assembly: System.Windows (in System.Windows.dll)
XMLNS for XAML: Not mapped to an xmlns.
Dependency property identifier field: FontWeightProperty
This property can select only from fonts that exist in a font family. It does not programmatically create alternative weights, with one exception: if a font family contains a regular weight and no bold weight, and you specify a bold weight. In this case, Windows Phone will simulate a bold weight by increasing the width of strokes by using a 2D graphic algorithm. Font fallback behavior does not change the property value, the property will remain as the value you set it to despite whatever visual behavior results due to font fallback.
The FontWeights values correspond to the usWeightClass definition in the OpenType specification. The usWeightClass represents an integer value between 1 and 999. Lower values indicate lighter weights, and higher values indicate heavier weights.