470447 proxy finder and checking software in .net

Need tool to download 3-4000 or more proxies (from free proxy sites) and then check to see if the proxy ip is passed using [login to view URL] and if so store the proxies that pass and filter them for timing. I have something similar in vb6, which gets the proxies and does simple check to see if Google accepts the proxy, but in this version in .net need to use threads to speed up checking and need to be able to show 1. proxies google accepts and 2 proxies where the ip address passes [login to view URL] (or other method to get L1 proxies).