Threading

Is this a college course question? The answer is: "because". Seriously, tho', there are safety issues around threading. I suspect the idea here is you can't write a value to a gui widget from a spawned thread, right? The gui thread retains ownership of all things in the original gui. Your threads are permitted to create new gui containers and controls (status bar on a popup form, a la File copy dialog in Windows) but the main gui is single threaded and greedy. The .Invoke and the delegate model gives you a nice way to inject your thread into that by way of passed values and still maintain thread safety. Feel free to pick up any number of books on threading to get more detailed technical theory and reasoning, but in a nutshell, it's all about safety and protection across thread boundaries.