1. 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.Text.RegularExpressions;
using System.Windows.Forms;
namespace Login
{
class Login
{
//decalre properties
public string Username { get; set; }
public string Userpassword { get; set; }
//intialise
public Login(string user, string pass)
{
this.Username = user;
this.Userpassword = pass;
}
//validate string
private bool StringValidator(string input)
{
string pattern = "[^a-zA-Z]";
if(Regex.IsMatch(input,pattern))
{
return true;
}
else
{
return false;
}
}
//validate integer
private bool IntegerValidator(string input)
{
string pattern = "[^0-9]";
if(Regex.IsMatch(input,pattern))
{
return true;
}
else
{
return false;
}
}
//clear user inputs
private void ClearTexts(string user, string pass)
{
user = String.Empty;
pass = String.Empty;
}
//method to check if eligible to be logged in
internal bool IsLoggedIn(string user, string pass)
{
//check user name empty
if (string.IsNullOrEmpty(user))
{

2. MessageBox.Show("Enter the user name!");
return false;
}
//check user name is valid type
else if (StringValidator(user) == true)
{
MessageBox.Show("Enter only text here");
ClearTexts(user,pass);
return false;
}
//check user name is correct
else
{
if (Username != user)
{
MessageBox.Show("User name is incorrect!");
ClearTexts(user,pass);
return false;
}
//check password is empty
else
{
if (string.IsNullOrEmpty(pass))
{
MessageBox.Show("Enter the passowrd!");
return false;
}
//check password is valid
else if (IntegerValidator(pass) == true)
{
MessageBox.Show("Enter only integer here");
return false;
}
//check password is correct
else if(Userpassword!=pass)
{
MessageBox.Show("Password is incorrect");
return false;
}
else
{
return true;
}
}
}
}
}
}
CompleteCsharp

3. 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;
namespace Login
{
public partial class MainForm : Form
{
public MainForm()
{
InitializeComponent();
}
//Enter code here for your version of username and userpassword
Login login = new Login("admin", "1234");
private void button1_Click(object sender, EventArgs e)
{
//define local variables from the user inputs
string user = nametxtbox.Text;
string pass = pwdtxtbox.Text;
//check if eligible to be logged in
if(login.IsLoggedIn(user,pass))
{
MessageBox.Show("You are logged in successfully");
}
else
{
//show default login error message
MessageBox.Show("Login Error!");
}
}
private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventAr
gs e)
{
//enter your code for forget password case
MessageBox.Show("Under development");
}
private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventAr
gs e)
{
//Enter your code for registration form of your choice
MessageBox.Show("Under development");
}
}
}