A simple WPF Authentication

Question

How to create a simple WPF Authentication for WPF application? For example: First time a user should registry then login. Users login and password should be saved as txt file(encrypted). If process of authentication is successful,then it should redirect to another existed window.

I'm a beginner in WPF. I've searched about this question,but didn't find what I need. I need a simple,step by step explanation of how to do it.

Thanks in advance! :)

Answer 1

I am also learning so in order to exercise a bit i have created a very simple example for you. It is probably unprofessional and unsafe but i think (hope) it is possible to extend it somehow :).

Firstly you need to create simple WPF windows (use txt/btn+Name naming convention):

For both windows add

using System.IO;

Then you need to add events for buttons and modify code for both windows:

public partial class LoginWindow : Window
{
    public LoginWindow()
    {
        InitializeComponent();
    }
    // This is really bad/weak encryption method
    String WeakDecryptMethod(String textIn)
    {
        Char[] temp = textIn.ToArray<Char>();
        for (int i = 0; i < textIn.Length; i++)
        {
            temp[i] = (char)((int)temp[i] - 3);
        }
        return new String(temp);
    }
    private void btnRegister_Click(object sender, RoutedEventArgs e)
    {
        RegisterWindow newWindow = new RegisterWindow();
        newWindow.ShowDialog();
    }
    private void btnOK_Click(object sender, RoutedEventArgs e)
    {
        // If file exist and login and password are "correct"
        if (File.Exists("Users.txt") 
            && txtLogin.Text.Length >= 4 
            && txtPass.Text.Length >= 4)
        {
            using (StreamReader streamReader = new StreamReader("Users.txt"))
            {
                // While there is something in streamReader read it
                while (streamReader.Peek() >= 0)
                {
                    String decryptedLogin = WeakDecryptMethod(streamReader.ReadLine());
                    String decryptedPass = WeakDecryptMethod(streamReader.ReadLine());
                    if (decryptedLogin == txtLogin.Text && decryptedPass == txtPass.Text)
                    {
                        ProtectedWindow protectedWindow = new ProtectedWindow();
                        this.Close();
                        protectedWindow.Show();
                        break;
                    }
                }
            }
        }
    }
    private void btnCancel_Click(object sender, RoutedEventArgs e)
    {
        this.Close();
    }
}

And code for Register window:

public partial class RegisterWindow : Window
{
    public RegisterWindow()
    {
        InitializeComponent();
    }
    // This is really bad/weak method to encrypt files
    String WeakEncryptMethod(String textIn)
    {
        Char[] temp = textIn.ToArray<Char>();

        for (int i = 0; i < textIn.Length; i++)
        {
            temp[i] = (char)((int)temp[i] + 3);
        }
        return new String(temp);
    }
    private void btnRegister_Click(object sender, RoutedEventArgs e)
    {
        // If file exist and login and password are "correct"
        if (File.Exists("Users.txt") 
            && txtLogin.Text.Length >= 4 
            && txtPass.Text.Length >= 4 
            && txtPass.Text == txtPassCheck.Text)
        {
            StringBuilder stringBuilder = new StringBuilder();
            using (StreamReader streamReader = new StreamReader("Users.txt"))
            {
                stringBuilder.Append(streamReader.ReadToEnd());
            }
            using (StreamWriter streamWriter = new StreamWriter("Users.txt"))
            {
                streamWriter.Write(stringBuilder.ToString());
                streamWriter.WriteLine(WeakEncryptMethod(txtLogin.Text));
                streamWriter.WriteLine(WeakEncryptMethod(txtPass.Text));
            }
            this.Close();
        }
    }
    private void btnCancel_Click(object sender, RoutedEventArgs e)
    {
        this.Close();
    }
}

In order to work application need to have access to file "Users.txt" which needs to be placed in the same folder.

Notes:

1. It will be better if you will use some proper encryption functions and probably create separate class for it. Additionally i am almost sure that it will not work properly with login and password which contains the last 3 characters from the end of ASCII tables.
2. In my opinion it is a bad idea to store login and password data in *.txt file :).
3. As far i know C# code is very easily reverse engineered so probably it will be better to hide encryption/decryption part somehow. I do not know much about it, but u will be able to read more [here] 2 and probably uncle Google will be able to help.
4. Code is very simple and there is probably a lot of possibilities to extend it (more file handling stuff, TextBox validation for proper input and password strength calculations)