MafiaTelegramBot/MafiaTelegramBot/Models/Commands/StartCommand.cs

using System.Threading.Tasks;
using MafiaTelegramBot.DataBase;
using MafiaTelegramBot.Resources;
using Telegram.Bot.Types;

namespace MafiaTelegramBot.Models.Commands
{
    public class StartCommand : Command
    {
        protected override string Name => "/start";

        public override async Task<Message> Execute(Update update)
        {
            if (await UserDao.UserExists(UserId))
            {
                var player = await UserDao.GetUserById(UserId);
                if (player.GetRoomKey() != "")
                    return await Bot.SendWithMarkdown2(ChatId, $"{strings.prefer_leave_from_room} {await player.GetRoomName()}");
                return await Bot.SendWithMarkdown2(ChatId, strings.start_message, Keyboards.MainMenu);
            } 
            var username = await Utilities.EscapeSpecific(update.Message.From.Username);
            var firstName = await Utilities.EscapeSpecific(update.Message.From.FirstName);
            var lastName = await Utilities.EscapeSpecific(update.Message.From.LastName);
            var user = new DataBase.User
            {
                Id = UserId, ChatId = ChatId, Username = username, NickName =  $"{firstName} {lastName}"
            };
            await UserDao.Update(user);
            return await Bot.SendWithMarkdown2(ChatId, strings.start_message, Keyboards.MainMenu);
        }
    }
}