How to send a POST request as data from a textbox form?

Question

C++ / C#

There is an application in C #, it has a textbox form from which, when the button is pressed, the entered data should be retrieved, and a POST request should be sent with them

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Collections.Specialized;
using System.Net;

namespace std
{
    public partial class Form1 : MetroFramework.Forms.MetroForm
    {

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void MetroTextBox1_Click(object sender, EventArgs e)
        {
            
        }

        private void BunifuButton1_Click(object sender, EventArgs e)
        {
            using (WebClient client = new WebClient())
            {
                byte[] response = client.UploadValues("http://ccылка.ru/api", new NameValueCollection() {
    { "phone", "тут должны быть данные из textbox" },
    { "message", "Hello world" },
    { "key", "key" },
  });

                string result = System.Text.Encoding.UTF8.GetString(response);
            }
        }
    }
}

Answer 1

And what exactly is the problem?
To take data from a textbox, this is the MetroTextBox1.Text property, and if there are problems with POST,
here are examples, study:
https://carldesouza.com/httpclient-getasync-postas...
https://csharp. hotexamples.com/en/examples/-/HttpC...