ip_location.cs

public class IpLocation
{
        public string domain { get; set; }

        public string address { get; set; }

        public string numAddress { get; set; }

        public string location { get; set; }
}

ip_location_service.cs

var response = await httpClient.PostAsync("http://ip.chinaz.com/ajaxsync.aspx?at=ip", new FormUrlEncodedContent(new[]
{
                new KeyValuePair<string, string>("ip", ip)
}));
var result =  await response.Content.ReadAsStringAsync();
return JsonConvert.DeserializeObject<IpLocation>(result.Trim('(', '[', ')', ']'));

save_to_excel.cs

var file = new FileInfo();
using (var package = new ExcelPackage(file))
{
                var workBook = package.Workbook;
                var worksheet = workBook.Worksheets.First();
                var cells = worksheet.Cells.Value as object[,];
                if (null == cells)
                {
                    Console.WriteLine("failed");
                    return;
                }
                var cache = new Dictionary<string, IpLocation>();
                for (var index = 1; index < cells.GetLength(0); index++)
                {
                    if (null == worksheet.Cells[index, 0].Value || null != worksheet.Cells[index, 3].Value) continue;
                    try
                    {
                        var ip = worksheet.Cells[index, 0].Value.ToString();
                        var location = cache.ContainsKey(ip) ? cache[ip] : GetLocation(httpClient, ip).Result;
                        worksheet.Cells[index, 2].Value = location.numAddress;
                        worksheet.Cells[index, 3].Value = location.location;
                        Console.WriteLine($"Finish {ip}");
                    }
                    catch (Exception exception)
                    {
                        Console.WriteLine(exception.Message);
                    }
                }
                package.Save();
}