This code example is part of a tutorial on CSharp Delegates Please find the relevant tutorial at this location, https://www.youtube.com/watch?v=jABhPwEfA-I&lc=UgwmqSpc8z0An7NSWVl4AaABAg If you download this project and run it you'll get an exception (this is because you'll need to run relevant EF Core migration commands to build a SQLite database) Once you have run the relvant migration commands, the code will run as expected Please go through the video tutorial first before running the code I explain how to run the relevant EF Core migration commands at around the 13:54 mark.