Question

I Made an application. The Main form Name is Form1.
And the other Form is called PoP.

public partial class pops : Form
{
    public pops()
    {
        InitializeComponent();
        CenterToScreen();
    }

    private void pops_Load(object sender, EventArgs e)
    {
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Close();
    }

    private void lblAdminNo_Click(object sender, EventArgs e)
    {
    }
}

Answer 1

Make two public properties on popup form and retrieve them from parent form.

string username = string.Empty;
string password = string.Empty;

using (LoginForm form = new LoginForm ())
 {
     DialogResult result = form.ShowDialog();
     if (result == DialogResult.Ok)
     {
         username = form.Username;
         password = form.Password;
     }
 }