.net - Multithreading Function To Implement Threads Fetching From A List Of Urls To Parse Content?

I have the following multithreading function to implement threads fetching from a list of urls to parse content. The code was suggested by a user and I just want to know if this is an efficient way of implementing what I need to do. I am running the code now and getting errors on all functions that worked fine doing single thread.for example now for the list that I use to check visited urls; I am getting the 'argumentoutofrangeexception - capacity was less than the current size'/Does everything now need to be synchronized?

Dim startwatch As New Stopwatch
Dim elapsedTime As Long = 0
Dim urlCompleteList As String = String.Empty

[code]...