Code of today lesson

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace firstProject
{
    public partial class win2 : Form
    {
        String str;
        dbEntities db = new dbEntities();
        public win2()
        {
            InitializeComponent();
        }
        public win2(String str)
        {
            this.str = str;
            InitializeComponent();

        }
        private void win2_Load(object sender, EventArgs e)
        {
            var tmp = (from s in db.customer select s).ToList();
            dataGridView1.DataSource = tmp;
            dataGridView1.ReadOnly = true;
            dataGridView1.Columns[0].Visible = false;
            dataGridView1.Columns[1].HeaderText = "שם פרטי";

            comboBox1.DataSource = tmp;
            comboBox1.DisplayMember = "firstName";
            comboBox1.ValueMember = "id";

        }

        private void button1_Click(object sender, EventArgs e)
        {
            customer x = new customer();
            x.firstName = textBox1.Text;
            x.lastName = textBox2.Text;
            x.phone = maskedTextBox1.Text;

            db.customer.AddObject(x);
            db.SaveChanges();
            MessageBox.Show("עודכן בהצלחה");
            textBox1.Text = "";
            textBox2.Text = "";
            win2_Load(sender, e);

        }

        private void pictureBox1_SizeChanged(object sender, EventArgs e)
        {

        }

        private void win2_SizeChanged(object sender, EventArgs e)
        {
            int x,y;
            x = this.Width;
            y = this.Height;
            

        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            customer c1 = (customer) comboBox1.SelectedItem;
            label1.Text = c1.phone;
        }
    }
}