GetRemoteIP - extension method on HttpRequestBase

GetRemoteIP.cs

public static string GetRemoteIP(this HttpRequestBase request, bool useForwardedForHeader = false)
        {
            if (request == null)
                throw new ArgumentNullException(nameof(request));

            const string FORWARDED_FOR = "HTTP_X_FORWARDED_FOR";
            const string REMOTE_ADDR = "REMOTE_ADDR";

            string ipAddress = null;

            if (useForwardedForHeader)
                ipAddress = request.ServerVariables[FORWARDED_FOR].Split(",".ToCharArray()).FirstOrDefault()?.Trim();

            if (string.IsNullOrEmpty(ipAddress))
                ipAddress = request.ServerVariables[REMOTE_ADDR];

            return ipAddress;
        }