Try using this C# IRC Library:
http://www.meebey.net/projects/smartirc4net/
It has many methods, I'm sure you can achieve everything you want with them:
http://smartirc4net.meebey.net/docs/0.4.0/html/
Projects using SmartIrc4net
- Smuxi IRC Client
- SparkleShare
- Low Orbit Ion Cannon
- MonkeyWrench
- U-Lyss IRC-Bot
- DG Network
- Abbot
- Spike.NET
- Prelude Chatbot
- VandalSniper
References: Get users list of a given channel in IRC server using C#