In order to change the Font of the whole ControlDefault theme, please follow these steps:
1. Open Visual Style Builder and select File >> Export Built-in Themes. This option will export all available predefined themes as theme packages.
2. In Visual Style Builder select File >> Open Package and select ControlDefault.tssp
3. In the Repository window, find the repository items related to SegoeUI font set their Font property to Microsoft Sans Serif
4. Save the package and load it in your project as described here
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