Add the eventhandler (_wc.DownloadStringCompleted
) before the web call.
Also since you are calling an async method you should be doing
await _wc.DownloadStringAsync(....
Otherwise it's not async at all, and the method should be written with the async keyword. I think you need to read up on your async knowledge.
Here's a good guide to go through: http://msdn.microsoft.com/en-us/library/hh191443.aspx