I wonder how, at the moment of page instance creation, how can I assign a value to some page's property, the value based on the folder name where this page instance is created?
Something related to '
public override void SetDefaultValues(ContentType contentType)'?
The SetDefaultValues method allows you to set default values for your content but this is executed before the content is saved in the repository. So you need to hook into the content created event: https://world.episerver.com/documentation/class-library/?documentId=cms/11/5B685F5 which would allow you to access the parent (folder) and update your content accordingly. You can do this in an Episerver intialisation module: https://world.episerver.com/documentation/developer-guides/CMS/initialization/Creating-an-initialization-module/