Fonts are a little weird because text is so different in Silverlight. For fonts that are not system fonts, you basically have two options, each with their benefits and drawbacks.
1. You can include the xnb file for the font instead of the spritefont file. This needs to be the xnb file generated from a
debug build of your XNA solution. This is the easiest way, but you don't get the benefits of vector graphics in Silverlight, and it has the extra build step of building your XNA project in
debug mode first.
2. You can include the SpriteFont file, but then you need to also include the ttf file in your project and you need to add an extra line of code that needs to be called on startup. There is an example of this in the SnakeGameSilverSprite sample in the SilverSprite
solution. Let's say this is your SpriteFont file:
<?xml version="1.0" encoding="utf-8"?>
This file contains an xml description of a font, and will be read by the XNA
Framework Content Pipeline. Follow the comments to customize the appearance
of the font in your game, and to change the characters which are available to draw
Modify this string to change the font that will be imported.
<FontName>Becker Black NF</FontName>
Size is a float value, measured in points. Modify this value to change
the size of the font.
Spacing is a float value, measured in pixels. Modify this value to change
the amount of spacing in between characters.
UseKerning controls the layout of the font. If this value is true, kerning information
will be used when placing characters.
Style controls the style of the font. Valid entries are "Regular", "Bold", "Italic",
and "Bold, Italic", and are case sensitive.
If you uncomment this line, the default character will be substituted if you draw
or measure text that contains characters which were not included in the font.
<!-- <DefaultCharacter>*</DefaultCharacter> -->
CharacterRegions control what letters are available in the font. Every
character from Start to End will be built and made available for drawing. The
default range is from 32, (ASCII space), to 126, ('~'), covering the basic Latin
character set. The characters are ordered according to the Unicode standard.
See the documentation for more information.
Then in Page.xaml.cs, add the following line to the code after the InitializeComponent call:
game.AddFont("Becker Black NF",
"./Becker Black NF.ttf#Becker Black NF"
where "game" is the name of the game element in the xaml. The first string in this call is the same as the FontName in the spritefont file, and the second is the font file information.
For your case this will probably be something like:
assuming that you add Kooten.ttf to the root of your Silverlight project and give it a build type of Resource.
Let me know if you still have issues after following these steps.