Add strings to string array

Question

class Myclass
{
    static string[] user_Name = { "admin", "user1", "user2" };
    static string[] user_Password ={ "admin", "123", "789" };

    public static void Check_Method(string u_name, string u_password)
    {

        for (int i = 0; i < user_Name.Length; i++)
        {
            if (u_name == user_Name[i] && u_password == user_Password[i])
            {
                MessageBox.Show("login successful");
                break;
            }
            else
            {
                if (i == (user_Name.Length - 1))
                    MessageBox.Show("Badshow");
            }
        }
    }
    public static void add_user(string name, string password)
    {
        i=user_Name.Length;
        user_Name[i]=name;
        user_Password[i]=password;
        //here i want to add another user but im unable to find the way
    }
}

But it gives an error that it is outside the boundary of an array.

What could be the most convenient way to perform this action?

Answer 1

Don't use arrays if you need variable sized storage.

Use List<string> instead - it allows you to Add items.

---

In your case, your choice of two arrays is questionable, as each user has a corresponding password - always. This suggests that you should have a custom class to hold a user/password pair.

With such a class (say User), you would hold a List<User> and simplify your code.

Answer 2

Try using a List<>.

class Myclass
{
    static List<string> user_Name = new List<string>{ "admin", "user1", "user2" };
    static List<string> user_Password = new List<string>{ "admin", "123", "789" };

    public static void Check_Method(string u_name, string u_password)
    {

        for (int i = 0; i < user_Name.Length; i++)
        {
            if (u_name == user_Name[i] && u_password == user_Password[i])
            {
                MessageBox.Show("login successful");
                break;
            }
            else
            {
                if (i == (user_Name.Length - 1))
                    MessageBox.Show("Badshow");
            }
        }
    }
    public static void add_user(string name, string password)
    {
        user_Name.Add(name);
        user_Password.Add(password);
    }
}

Here's a refactored version:

Users are contained in a user class.

They are IEquatable<> which compares their username/passwords (you might want to consider looking into a Guid to keep them unique).

Easily add/remove users.

public class User : IEquatable<User>
{
    public User(string name, string password)
    {
        Name = name;
        Password = password;
    }

    public string Name { get; set; }
    public string Password { get; set; }

    public bool Equals(User other)
    {
        if (other == null) return false;

        return other.Name == Name && other.Password == Password;
    }
}

public class AuthenticationManager
{
    private List<User> LoggedInUsers = new List<User>
    { new User("Admin", "admin"), new User ("user1", "123"), new User ("user2", "789") };

    public bool Authenticate(string userName, string password)
    {
        var user = new User(userName, password);

        //if the user is in the list it will return false otherwise true.
        return !LoggedInUsers.Any(u => user.Equals(user)); 
    }

    public void Login(string name, string password)
    {
        LoggedInUsers.Add(new User(name, password));
    }

    public void Logout(string name, string password)
    {
        LoggedInUsers.Remove(new User(name, password));
    }
}