How do I find the local IP address on a Win 10 UWP project

Use this to get host IPaddress in a UWP app, I've tested it:

    foreach (HostName localHostName in NetworkInformation.GetHostNames())
    {
        if (localHostName.IPInformation != null)
        {
            if (localHostName.Type == HostNameType.Ipv4)
            {
                textblock.Text = localHostName.ToString();
                break;
            }
        }
    }

And see the API Doc here

You may try like this :

private string GetLocalIp()
{
    var icp = NetworkInformation.GetInternetConnectionProfile();

    if (icp?.NetworkAdapter == null) return null;
    var hostname =
        NetworkInformation.GetHostNames()
            .SingleOrDefault(
                hn =>
                    hn.IPInformation?.NetworkAdapter != null && hn.IPInformation.NetworkAdapter.NetworkAdapterId
                    == icp.NetworkAdapter.NetworkAdapterId);

    // the ip address
    return hostname?.CanonicalName;
}

the answer above is also right