MulticastOption.cs

namespace System.Net.Sockets
{
    public class MulticastOption
    {
        private IPAddress group;

        private IPAddress localAddress;

        private int ifIndex;

        public IPAddress Group
        {
            get
            {
                return group;
            }
            set
            {
                group = value;
            }
        }

        public IPAddress LocalAddress
        {
            get
            {
                return localAddress;
            }
            set
            {
                ifIndex = 0;
                localAddress = value;
            }
        }

        public int InterfaceIndex
        {
            get
            {
                return ifIndex;
            }
            set
            {
                if (value < 0 || value > 16777215)
                {
                    throw new ArgumentOutOfRangeException("value");
                }
                localAddress = null;
                ifIndex = value;
            }
        }

        public MulticastOption(IPAddress group, IPAddress mcint)
        {
            if (group == null)
            {
                throw new ArgumentNullException("group");
            }
            if (mcint == null)
            {
                throw new ArgumentNullException("mcint");
            }
            Group = group;
            LocalAddress = mcint;
        }

        public MulticastOption(IPAddress group, int interfaceIndex)
        {
            if (group == null)
            {
                throw new ArgumentNullException("group");
            }
            if (interfaceIndex < 0 || interfaceIndex > 16777215)
            {
                throw new ArgumentOutOfRangeException("interfaceIndex");
            }
            Group = group;
            ifIndex = interfaceIndex;
        }

        public MulticastOption(IPAddress group)
        {
            if (group == null)
            {
                throw new ArgumentNullException("group");
            }
            Group = group;
            LocalAddress = IPAddress.Any;
        }
    }
}