如何更改仅适用于正确用户的存储在文本文件中的用户名和密码

Question

i am currently making a application for my a level computing coursework. for my coursework i am required to make a login and registration system which requires me to store the user details in a text file this is only for my coursework so security isent important. my registration and login system works fine but i am also required to have a change account details screen in which the user can change their username and password.

my problem is that my code that i have currently changes the password for every user with the same password ie if 2 users have password123 as a password both their passwordds gets changed to the new password

 private void btnUpdatePassword_Click(object sender, EventArgs e)
    {
        string oldusername = txtBoxOldUsername.Text;
        string newusername = txtBoxNewUsername.Text;
        string oldpassword = txtBoxOldPassword.Text;
        string newpassword = txtBoxNewPassword.Text;

        string text = File.ReadAllText("users.txt");
        text = text.Replace(oldpassword, newpassword).Replace(oldusername, newusername);
        File.WriteAllText("users.txt", text);
    }

my problem is that i dont know how to change the password for only the correct user. it would be great if anyone could help thanks. also i HAVE to use a text file to do this meaning i cant use jason on xml etc

this is what my text file looks like

first user ~username~password

second user ~username123~password

third user ~username1234~password

and this is the code i use to write to the text file

FileStream fileStream = new FileStream("users.txt", FileMode.Append, FileAccess.Write);
                        StreamWriter streamWriter = new StreamWriter(fileStream);

                        try
                        {
                            streamWriter.WriteLine(fullname + "~" + username + "~" + password + "~" + lastlogin);

                            MessageBox.Show("User registered successfully", "Registration Successful");

                            this.Hide();
                            var homeForm = new HomeForm();
                            homeForm.Closed += (s, args) => this.Close();
                            homeForm.Show();

                        }
                        catch (Exception)
                        {
                            MessageBox.Show("Error registering the user", "Please try again");
                        }
                        finally
                        {
                            streamWriter.Close();
                            fileStream.Close();
                        }

Answer 1

Here is an idea on how to implement it. My first suggestion is to add a comma deliminator to your text file so your values in users.txt will be in the following form

second user~username123~password,
third user~username1234~password,
first user~username~smelly,

Import all the users from users.txt at once and split them by our deliminator ','

 var users = File.ReadAllText(@"C:\users.txt").Split(',').ToList().Where(x=> !String.IsNullOrWhiteSpace(x));

Note this clause .Where(x=> !String.IsNullOrWhiteSpace(x ) will be needed because when I rewrite the file , for simplicity sake I add a comma to each entry. As last entry will have a comma we end up with an extra empty object. This clause will rectify it.

Create a class which will contains all the user properties:

    private class User
    {
        public string Name { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }

        public string PrepareForFile()
        {
            return Name + "~" + UserName + "~" + Password + ",";
        }
    }

Loop through all the retrieved users information from file and build a list of user:

        List<User> myUsers = new List<User>();
        foreach (var user in users)
        {
            var information = user.Split('~');
            User temp = new User();
            temp.Name = information[0].Trim();
            temp.UserName = information[1].Trim();
            temp.Password = information[2].Trim();
            myUsers.Add(temp);
        }

Now you have a manageable structure and you can perform all the desired operations. Once finished use the method PrepareForFile() to create a string like second user~username123~password to be written into file.

Putting it all together(this is a console app):

  static class Program
    {
        private class User
        {
            public string Name { get; set; }
            public string UserName { get; set; }
            public string Password { get; set; }

            public string PrepareForFile()
            {
                return Name + "~" + UserName + "~" + Password + ",";
            }
        }

        static void Main(string[] args)
        {
            var users = File.ReadAllText(@"C:\users.txt").Split(',').ToList().Where(x=> !String.IsNullOrWhiteSpace(x));

            List<User> myUsers = new List<User>();
            foreach (var user in users)
            {
                var information = user.Split('~');
                User temp = new User();
                temp.Name = information[0].Trim();
                temp.UserName = information[1].Trim();
                temp.Password = information[2].Trim();
                myUsers.Add(temp);
            }

            var selectedUser = myUsers.Where(x => x.UserName == "username").SingleOrDefault();
            myUsers.Remove(selectedUser);
            selectedUser.Password = "Leo";
            myUsers.Add(selectedUser);

            List<string> formatForFile = new List<string>();
            foreach(var item in myUsers)
            {
                formatForFile.Add(item.PrepareForFile());
            }
            File.WriteAllLines(@"C:\users.txt", formatForFile.ToArray());
        }
    }

Changing username1234 password from "password" to "AlexLeo":

Before

After

Answer 2

You can store the username with the password when saving the password and delete the username when it is extracted from the password and add the username when adding the password. for example:

private void btnUpdatePassword_Click(object sender, EventArgs e)
{
    string oldusername = txtBoxOldUsername.Text;
    string newusername = txtBoxNewUsername.Text;
    string oldpassword = txtBoxOldPassword.Text;
    string newpassword = txtBoxNewPassword.Text;

    string text = File.ReadAllText("users.txt");
    text = text.Replace(oldpassword + oldusername, newpassword + newusername).Replace(oldusername, newusername);
    File.WriteAllText("users.txt", text);
}

Answer 3

Based on your updated OP

string str = System.IO.File.ReadAllText(fileName);
var users = str.Split(new []{Environment.NewLine},StringSplitOptions.RemoveEmptyEntries)
            .Select(x=>
            {
              var strArray = x.Split(new []{"~"},StringSplitOptions.RemoveEmptyEntries);
              return new 
               { 
                 FirstName = strArray[0],
                 User = strArray[1],
                 Password = strArray[2]
               };
            }
            );

var usernameToUpdate = "username123";
var newPassword = "Thisisnewpassword";

var updatedList = users.Select(x => x.User.Equals(usernameToUpdate) ? 
                        $"{x.FirstName} ~{x.User}~{newPassword}"
                        : $"{x.FirstName} ~{x.User}~{x.Password}").ToList();

var newFileData = String.Join(Environment.NewLine, 
                   updatedList);
File.WriteAllText(fileName, newFileData);