There are lots of ways to do this if you google it, but a popular way is to use
Thread
s
Make sure you have this namespace included.
using System.Threading;
Then in the function where you normally call
fetchData()
insert this snippet.
Thread background = new Thread(() => fetchData());
background.Start();
Then make sure at the end of your
fetchData()
you make a Thread-Safe Call to end the Progressbar marquee or whatever you'd like.