我们可以在没有任何第三方工具的情况下通过C#应用程序在whats应用程序上发送消息吗？

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

class Program
{
    static async Task Main(string[] args)
    {
        string phoneNumber = "目标手机号";
        string message = "你好，这是通过C#应用程序发送的消息！";

        string apiUrl = "https://api.whatsapp.com/send?phone=" + phoneNumber + "&text=" + Uri.EscapeDataString(message);

        using (HttpClient client = new HttpClient())
        {
            HttpResponseMessage response = await client.GetAsync(apiUrl);
            if (response.IsSuccessStatusCode)
            {
                Console.WriteLine("消息发送成功！");
            }
            else
            {
                Console.WriteLine("消息发送失败：" + response.ReasonPhrase);
            }
        }
    }
}