<Application.Resources>
    <FontFamily x:Key="HandWrite">
      pack://application:,,,/Resources/FontFamily/#apple cider daydreams
  </FontFamily> <!--#加字体名，不是字体文件名。字体名打开字体文件可得-->
</Application.Resources>

<TextBlock Foreground="White" FontFamily="{StaticResource HandWrite}" Text="GegSYS" />