This class specifies an IP address for IP-multicast packets. IP-multicast addresses must be in the range of 224.0.0.0 to 239.255.255.255. The MulticastOption is set on a socket using the SocketOptionName.AddMembership value with Socket.SetSocketOption( ). You can drop multicast with SocketOptionName.DropMembership.

public class MulticastOption {
// Public Constructors
   public MulticastOption(System.Net.IPAddress group);
   public MulticastOption(System.Net.IPAddress group, System.Net.IPAddress mcint);
// Public Instance Properties
   public IPAddress Group{set; get; }
   public IPAddress LocalAddress{set; get; }
}