need an input on how to connect to active directory using specific lan connection

Domain Abc -> connection 1 Domain xyz -> connection 2

i have 2 nic card which connects to diff network. at this moment we use virtual image when we need to check /reset any account on active directory for a specific xyz.

i have wrote a small app which allows me to access AD (ABC) which use connection 1

on net i came across and have gone through Socket Class (System.Net.Sockets) / System.Net.Sockets Namespace and before do more research/reading

can anyone suggest what is the way to bind it connection 2 using .net