using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        //
        // Delivery of Message to Send to SMS HTTPS API (.Net 6 version)
        //
        
        var postVars = new List<string>();
        postVars.Add("Sender=" + Uri.EscapeDataString("youruser@yourdomain.com"));
        postVars.Add("Token=" + Uri.EscapeDataString("YourToken"));
        postVars.Add("Number=" + Uri.EscapeDataString("TheMobileRecipient"));
        postVars.Add("Message=" + Uri.EscapeDataString("Your SMS Message"));
        postVars.Add("MessageID=" + Uri.EscapeDataString("YourInternalMessageID"));

        var url = "https://api.tnz.co.nz/api/v2.03/HttpApi/SMS";
        var request = string.Join("&", postVars);

        using (var client = new HttpClient())
        {
            var content = new StringContent(request, Encoding.UTF8, "application/x-www-form-urlencoded");
            var response = await client.PostAsync(url, content);
            response.EnsureSuccessStatusCode();
            var responseContent = await response.Content.ReadAsStringAsync();
            Console.WriteLine(responseContent);
        }
    }
}