Attempting to set StartupProjectPath to an invalid .aprx path will be ignored. Set StartupOption to StartProjectMode.WithDefaultProjectafter setting the StartupProjectPath (to use the StartupProjectPath at start-up). Attempting to set the StartupOption to StartProjectMode.WithDefaultProject before the StartupProjectPath contains a valid .aprx path will be ignored. Conversely, attempting to set the StartupProjectPath back to null or empty string will be ignored if StartupOption is currently set to StartProjectMode.WithDefaultProject. The StartupOption must be changed to a different start mode first.
Requirements
Target Platforms: Windows 11, Windows 10, Windows 8.1