Login Form using Class in C# through File Stream

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using System.Collections;
namespace Win_Practice
{
    public class LoginClass
    {
        public void getdata()
        {
            string login, pass;
            TextReader tr;
            // refferene of file >> C:\Users\Zeeshan\Documents\Visual Studio 2012\Projects\Win_Practice\Win_Practice\bin\Debug
            using(tr = new StreamReader("Pass.txt"))
            {
                login = tr.ReadLine();
                pass = tr.ReadLine();
            }
            if (Frm_login.a == login && Frm_login.b == pass)
            {
                // Frm_login alpha = new Frm_login();
                // showing option form after successfull login
                Form2 f2 = new Form2();
                f2.Show();
            }
            else if (Frm_login.a == "" || Frm_login.b == "")
            {
                MessageBox.Show("User id or password is missing");
            }
            else if (Frm_login.a != login || Frm_login.b != pass)
            {
                MessageBox.Show("Invalid ID or Password");
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Win_Practice
{
    public partial class Frm_login: Form
    {
        public static string a, b;
        public Frm_login()
        {
            InitializeComponent();
        }
        public void btnSave_Click(object sender, EventArgs e)
        {
            a = tbUserId.Text;
            b = tbPass.Text;
            LoginClass beta = new LoginClass();
            beta.getdata();
        }
        public void Frm_login_Load(object sender, EventArgs e)
        {}
    }
}