How to click button stop when button start is running loop

See more:

C#

browser

chrome

, +

I have program that have start and stop
start button that is run instead loop:
-first loop change proxy then open browser .
-second loop open urls in chrome browser that opened in first iteration.

stop button:

I want it stop loop and reset .

I can't press in stop button while start button is running.

What I have tried:

I tried background

1-
http://stackoverflow.com/questions/3065700/how-to-start-and-stop-a-continuously-running-background-worker-using-a-button

I can press stop but i can't see chrome browser

2-

http://stackoverflow.com/questions/27580241/breaking-from-a-loop-with-button-click-c-sharp

I but my code instead of
Console.WriteLine("Hello, world");
when i debug code i see it does't run code in
_worker.DoWork += new DoWorkEventHandler((state, args) =>
{ });
and select it with yellow color.