Showing an updated list in a form

Question

I'm designing a database to hold a list of employees which is reading from a text file. I have two forms, the first one (frmManager) acts as a view to go through the list, which i have next and previous buttons which i scroll through the employees in the list. The other form(frmAdd), can add new employees to the List. My problem is, when i update the List<>, how can i update it in frmManager? when i add a new employee, theiir attributes get written to the text file but I have to rebuild the project to show the updated list. file that adds employees:

public class EmployeeDB
{
    public List<Employee> employees;

    public static EmployeeDB instance;

    public static EmployeeDB Instance
    {
        get
        {
            if (instance == null)
            {
                instance = new EmployeeDB();
                instance.populate();
            }
            return instance;
        }
    }

    public EmployeeDB()
    {
        employees = new List<Employee>();
    }

    public void populate()
    {
        string[] parts;
        foreach (string line in File.ReadAllLines("StaffList.txt"))
        {
            parts = line.Split(',');
            employees.Add(new Employee(parts[0], parts[1], parts[2], parts[3], int.Parse(parts[4]), int.Parse(parts[5])));

        }
    }
}

The employee class contains just a constructor to add their details. the form to add new employees

public partial class frmAdd : Form
{

    EmployeeDB employee;
    int grade;

    public frmAddEmployee()
    {
        employee = EmployeeDB.Instance;
        InitializeComponent();
    }

    private void btnCreate_Click(object sender, EventArgs e)
    {
        System.IO.StreamWriter file = new System.IO.StreamWriter("StaffList.txt", true);

        foreach (Employee em in employee.employees) //To avoid username clashes
        {
            if (em.username == txtUsername.Text)
            {
                file.WriteLine(txtFName.Text + "," + txtLName.Text + "," + txtUsername.Text + employee.employees.Count()
                               + "," + txtPassword.Text + "," + checkedButton().ToString() + ","
                              + 0.ToString(), Environment.NewLine);
            }
            else
            {
                file.WriteLine(txtFName.Text + "," + txtLName.Text + "," + txtUsername.Text
                                        + "," + txtPassword.Text + "," + checkedButton().ToString() + ","
                                       + 0.ToString(), Environment.NewLine);
            }

            file.Close();
            MessageBox.Show("Employee successfully added");
            return;
        }

I have tried recalling the EmployeeDB file hoping it would repopulate to no avail. Any help will be much appreciated.

Answer 1

You are not adding the new Employee to the list anywhere. From the code you included, you are only populating the list via populate().

I would add the new Employee to the EmployeeDB on button click. This will cause the list to be up-to-date. Then I would add a method to your EmployeeDB class that writes the file.

private void btnCreate_Click(object sender, EventArgs e)
{
    string username = txtUsername.Text;
    int i = employee.employees.Count();
    while (employee.AsEnumerable().Select(r => r.username == username).Count() > 0)
    {
        username = txtUserName.Text + i++;  //Makes sure you have no common usernames
    }
    employee.employees.Add(new Employee(){...});
    employee.SaveFile(); //New method  
}

I am assuming you have a string in the class Employee called username hence the r => r.username above