Send SMS with 🏗️ ASP.NET

// 1 — PRIMARY — use this
https://www.isms.com.my/isms_send_all_id.php
// 2 — Mirror — backup only
https://smtpapi2.vocotext.com/isms_send_all_id.php
// 3 — Mirror — backup only
https://smtpapi.vocotext.com/isms_send_all_id.php
// 4 — Mirror — backup only
https://ww3.isms.com.my/isms_send_all_id.php

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Net.Http;
using System.Threading.Tasks;

[ApiController]
[Route("api/[controller]")]
public class SmsController : ControllerBase
{
    // Register IHttpClientFactory in Program.cs: builder.Services.AddHttpClient();
    private readonly IHttpClientFactory _clientFactory;

    public SmsController(IHttpClientFactory clientFactory)
        => _clientFactory = clientFactory;

    [HttpPost("send")]
    public async Task<IActionResult> SendSms(string mobile, string message)
    {
        var payload = new Dictionary<string, string>
        {
            { "un",         "your_username" },
            { "pwd",        "your_password" },
            { "dstno",      mobile          },  // Full international format
            { "msg",        message         },
            { "type",       "1"             },  // 1 = ASCII, 2 = Unicode
            { "agreedterm", "YES"           },
            { "sendid",     "MyBrand"       }   // Optional, max 11 chars
        };

        var client   = _clientFactory.CreateClient();
        var response = await client.PostAsync(
            "https://www.isms.com.my/isms_send_all_id.php",
            new FormUrlEncodedContent(payload));

        var result = await response.Content.ReadAsStringAsync();

        if (result.StartsWith("2000"))
        {
            var trxId = result.Split(':')[1];
            return Ok(new { success = true, transactionId = trxId });
        }

        return BadRequest(new { success = false, error = result });
    }
}