I have a problem with my laptop where I connect to my home network and my work network, and my school network … and I have to use different proxy settings for Windows internet connection settings (which are used by virtually all .Net apps, including PowerShell) by default…

Of course, there are a lot of different apps that can manage those settings (and more) automatically using Windows NLA to trigger. However, I have an extra special requirement: when I plug in at work or at home, I want to run Synergy on the laptop as a client … but the name and ip of the host is different, of course — so I need to stop synergy and restart it with a different server name … something I can easily accomplish from a script or batch file … but changing proxies is a bit trickier.

I thought it would a simple call to a .Net library method, but after much searching, the only way of setting or retrieving Internet options seems to be through the old WinInet API, using InternetSetOptions (or InternetQueryOption to read them). Of course, to use these, you have to map the INTERNET_PER_CONN_OPTION_LIST and INTERNET_PER_CONN_OPTION structures to C#, and do whole lot of marshalling and manual memory management.

I did find some C# mappings for the Option structure on PInvoke.net but not for the others. I actually started writing them all by hand and then found a “recipe” in the (see the examples link) C# 3.0 Cookbook for retrieving Internet settings which had versions of all the structures I needed, as well as definitions for the flags I wanted. So… without further ado, let me share the code with you … (more…)