Answer - C# Event Handling Exercises

Qu: Write a program for Online Attendance. The conditions are as follow:
  1. User provides their name as Input and then application show message to “Welcome to their Name”.
  2. Jack, Steven, and Mathew are banned for the organization. So, when any user enters Jack, Steven, and Mathew as username, the application raised an event and fire alarm as well as sends email to administration.
Answer
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Online_Application
{
    class Program
    {
        static void Main(string[] args)
        {
            EnterName ename = new EnterName();
            ename.ev_BannedUser += WarningAlarm;
            ename.User();
            Console.Read();
        }
        static void WarningAlarm(object sender, BannedUserEventArgs e)
        {
            Console.WriteLine("{0} Users Found. Sending Email to Administration.", e.Name);
            Console.WriteLine("Email Sent.");
            Console.WriteLine("Warning Alarm Started.");
            Console.WriteLine("Press Ctrl + c to stop the alarm");
            for (;;)
            {
                Console.Beep();
                System.Threading.Thread.Sleep(100);
            }
        }
    }

    public class EnterName
    {
        public event EventHandler<BannedUserEventArgs> ev_BannedUser;
        public void User()
        {
            Console.Write("Enter You Name : ");
            string user = Console.ReadLine();

            if ((user == "Jack" || user == "Steven" || user == "Mathew") && (ev_BannedUser!=null))
            {
                ev_BannedUser(this, new BannedUserEventArgs(user));
            }
            else
            {
                Console.WriteLine("Welcome to " + user);
            }
        }
    }

    public class BannedUserEventArgs : EventArgs
    {
        public BannedUserEventArgs(string s)
        {
            Name = s;
        }
        public string Name { get; set; }
    }
}

When this program gets executed and user enters any of the banned user name, the program started beeping for infinite time. You must press ctrl + c to stop this beep sound.

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