I want to call an external dll file in Uipath Studio, but I don’t know how to implement it, I hope I can get some help, thank you！
I don’t think this is directly possible. You could probably build a custom activity for that though.
What is your usecase? Have you tried creating a custom activity, like @loginerror suggested https://docs.uipath.com/activities/docs/creating-a-custom-activity