使用WMI / Win32_NetworkAdapterConfiguration轮询C＃中的IP地址更改

Question

I'm making a program that needs to set a static IP to a computer's wired NIC, and the program can't perform the next part (querying an SNMP string from another IP on the same network) until it's positively set and usable, which experience has taught me isn't always instant. This program is written in C# on VS2013 as a WinForms application, and the function is below. The actual setting of the IP address works perfectly, the problem is trying to poll for when the change completes. I can run the program, have it set an IP address (never more than a single IP/Subnet/Gateway), and while it's still polling for the change, pop open a command prompt, run ipconfig, and see that the change has already gone through. The program will continue to hang until it times out. I have tried several different methods of querying and checking the IP addresses, including reassigning NICConfig every time through the loop and checking to see if any IP addresses in either string[] match, nothing works. I have not yet piped currentIPs[0] into a file or command line to see what it contains, but I strongly suspect it will contain the previous IP address. I also tried setting the IP address in the registry, per this post: Why does applying a static IP address via WMI work just once? but all that did for me was give me a second IP address on that interface in ipconfig with the program still hanging.

Actually, on further examination, it looks like the behavior is to add the IP address/subnet/gateway to the list (string array), instead of replacing the old info, but the program isn't even getting an updated version of the list with the intended IP on it. This may not have started until after messing with the registry values using code from the above link, I can't be sure. I also can't seem to remove the extra IPs from my PC's configuration, they don't show up in the windows ipv4 configuration page (but I do get a warning when closing it about multiple gateways), and removing them from the registry seems to do nothing - so any help fixing my computer's NIC configuration would also be appreciated.

private bool set_staticIP(string Index, string[] IP, string[] Subnet, string[] Gateway, string[] DNS)
{
    string WMIQuery = String.Format("Win32_NetworkAdapterConfiguration.Index='{0}'", Index);
    ManagementObject NICConfig = new ManagementObject(@"root\CIMV2", WMIQuery, null);
    ManagementBaseObject inParams = null;
    ManagementBaseObject outParams = null;

    string[] OldIP = (string[])NICConfig["IPAddress"];

    try
    {
        /* Set IP/Subnet mask */
        inParams = NICConfig.GetMethodParameters("EnableStatic");
        inParams["IPAddress"] = IP;
        inParams["SubnetMask"] = Subnet;

        outParams = NICConfig.InvokeMethod("EnableStatic", inParams, null);

        if (outParams["ReturnValue"].ToString() != "0")
        {
            MessageBox.Show("Error setting IP, returned " + outParams["ReturnValue"]);
        }

        /* Set Gateway(s) */
        inParams = NICConfig.GetMethodParameters("SetGateways");
        inParams["DefaultIPGateway"] = Gateway;
        inParams["GatewayCostMetric"] = new int[] {1};

        outParams = NICConfig.InvokeMethod("SetGateways", inParams, null);

        if (outParams["ReturnValue"].ToString() != "0")
        {
            MessageBox.Show("Error setting Gateway, returned " + outParams["ReturnValue"]);
        }

        /* Set DNS Servers */
        inParams = NICConfig.GetMethodParameters("SetDNSServerSearchOrder");
        inParams["DNSServerSearchOrder"] = DNS;
        outParams = NICConfig.InvokeMethod("SetDNSServerSearchOrder", inParams, null);

        if (outParams["ReturnValue"].ToString() != "0")
        {
            MessageBox.Show("Error setting DNS, returned " + outParams["ReturnValue"]);
        }

        bool IPMatches = false;
        string[] currentIPs = null;
        int timeout = 2000;
        int i;

        for (i = 0; i < timeout && !IPMatches; i++)
        {
            currentIPs = (string[])NICConfig["IPAddress"];
            if (currentIPs == IP || currentIPs != OldIP)
            {
                IPMatches = true;
                break;
            }
            Task.Delay(100);
        }
        if (i >= timeout)
        {
            MessageBox.Show("Timeout while setting static IP address");
        }

    }
    catch(ManagementException e)
    {
        MessageBox.Show("set_static() threw exception " + e.Message);
    }

    return IPMatches;
}

The machines I've tested this on are a laptop running Windows 7 x64, I get the same behavior with the internal NIC and a USB NIC, and a tablet running Windows 8.1 x64 with the same USB NIC.

Answer 1

You can use:

// Callback für Netzwerk-Änderungen erzeugen
NetworkChange.NetworkAddressChanged += new NetworkAddressChangedEventHandler(AddressChangedCallback);

// Callback für Netzwerk-Änderungen
void AddressChangedCallback(object sender, EventArgs e)
{
    // IP is changed;
}

You will get the callback whenever a network adress is changed. Now you can check if it is the adress you are waiting for.