在c＃bot中按用户ID发送消息

Question

i'm trying to send message to People user name for example my friends username is @... but no thing happend no Error and no send can i use this library ? or just with tlsharp? how can i found apiid and hashid for my bot?

using Telegram.Bot;

and

 public partial class Form1 : Form
    {
       Telegram.Bot. TelegramBotClient bot = new TelegramBotClient("token");

        Thread a;
             public Form1()
        {
            InitializeComponent();
        }


        public void GetUpdates()
        {
            int offset = 0;
            while (true)
            {

                Telegram.Bot.Types.Update[] updates = 
                 bot.GetUpdatesAsync(offset).Result;

                foreach (var update in updates)
                {

                    offset = update.Id + 1;
                    if (update.Message == null)
                        continue;

                    var from = update.Message.From.FirstName;
                    var text = update.Message.Text;
                   string  chatid = update.Message.Chat.Id;
                    string username = update.Message.From.Username;
                    // label1.BeginInvoke(delegate { label1.Text = label1.BeginInvoke(delegate { label1.Text = string.Format("sender:{0}\ntext:{1}\ncatid:{2}", from, text, chatid); }); });
                  // lblshow.Text = string.Format("sender:{0}\ntext:{1}\ncatid:{2}", from, text, chatid);
                  //label1.Text = string.Format("sender:{0}\ntext:{1}\ncatid:{2}", from, text, chatid);
                    this.BeginInvoke((System.Windows.Forms.MethodInvoker)delegate () {textBox1.Text = string.Format("sender:{0}\ntext:{1}\ncusername:{2}", from, text, username); });
                  bot.SendTextMessageAsync( chatid, "سلام بر شما");
                    //is this correct for send to people? 
                    bot.SendTextMessageAsync("@Hoda.....", "hi");


                }




            }

Answer 1

you cant send message to user by user Name.telegram bot API only accept user Id. (except channels).

Answer 2

When you try to send messages to users you must know their chatID (chatID is a long number which is unique for every user in telegram and never changes while username can be changed) or you must have stored their chatIDs in a database or a file or ...

This means a user must have sent at least one message to your bot before this includes the /start command . Then your bot can find out their chatID and using that chatID, you can send whatever you want to that user unless he/she has blocked your bot by pressing Delete and Stop button when trying to delete the conversation between him/her and your bot.