Binding an IP address just works for the first time

Question

I want to make a web request from one of available IP addresses on server so I use this class:

public class UseIP
{
    public string IP { get; private set;          


        

Answer 1

I like this new class UseIP.

There is a point at Specify the outgoing IP Address to use with WCF client about protecting yourself from IPv4/IPv6 differences.

The only thing that would need to change is the Bind method to be like this:

private IPEndPoint Bind(ServicePoint servicePoint, IPEndPoint remoteEndPoint, int retryCount)
{
    if ((null != IP) && (IP.AddressFamily == remoteEndPoint.AddressFamily))
        return new IPEndPoint(this.IP, 0);
    if (AddressFamily.InterNetworkV6 == remoteEndPoint.AddressFamily)
        return new IPEndPoint(IPAddress.IPv6Any, 0);
    return new IPEndPoint(IPAddress.Any, 0);
}

re: the Bind method being called multiple times.

What works for me is to remove any delegate link before I add it.

ServicePoint servicePoint = ServicePointManager.FindServicePoint(uri);
servicePoint.BindIPEndPointDelegate -= this.Bind;   // avoid duplicate calls to Bind
servicePoint.BindIPEndPointDelegate += this.Bind;

I also like the idea of caching the UseIP objects. So I added this static method to the UseIP class.

private static Dictionary _eachNIC = new Dictionary();
public static UseIP ForNIC(IPAddress nic)
{
    lock (_eachNIC)
    {
        UseIP useIP = null;
        if (!_eachNIC.TryGetValue(nic, out useIP))
        {
            useIP = new UseIP(nic);
            _eachNIC.Add(nic, useIP);
        }
        return useIP;
    }
}