如何使用C＃asp.net获取系统IP（IPv4）地址并转换为字符串

Question

On my web application I am using the following function to get System IP

Function

public void SetHostid()
    {
        try
        {
            string ip = "";
            string strHostName = "";
            strHostName = System.Net.Dns.GetHostName();

            IPHostEntry ipEntry = System.Net.Dns.GetHostEntry(strHostName);

            IPAddress[] addr = ipEntry.AddressList;

            ip = addr[1].MapToIPv4().ToString();

            HostId = ip;
            HttpContext.Current.Session["Hostid"] = HostId;
        }
        catch (Exception ex)
        {
            Error_ManagerClass em = new Error_ManagerClass();
            em.WriteError(ex);
        }
    }

It works perfectly because the IP is on the 1 postion of the variable addr ( addr[ 1] ).

And the problem comes when I try to run the same solution from a different system. function throws an error while trynig to convert IP to string( ip = addr[1].MapToIPv4().ToString(); ) because IP is not in the position number 1.

how can I change the function to work on every computer ??

Answer 1

If you want to get IPv4 only use this code:

var addr = ipEntry.AddressList.Where(ip => ip.AddressFamily == AddressFamily.InterNetwork);

var firstInList = addr.First(); // get first

But you should consider which IP to chose when there are several IP addresses in system.