That's why you should use asynchronous methods. You simply call the method on the UI thread and it goes off on it's merry way, not hogging resources or freezing the UI, and you can get on with whatever else you need to do. When the background task is done a callback is invoked on a secondary thread and you can complete the task. You can then delegate back to the UI thread to update the display if required.

You should check out that code of mine if you haven't already. You're welcome to just reference my DLL as is if you want, which would require nothing more from you than calling some methods and handling some events. Otherwise you can get some ideas from my code to implement in your own.