con.Open() why not working?

Question

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Data.SqlClient;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace WindowsFormsApp10

{

public partial class Form1 : Form

{

String path = @"Data Source = DESKTOP - 2PC2RB2\SQLEXPRESS; Initial Catalog = edu; Integrated Security = True";

SqlConnection con;

public Form1()

{

InitializeComponent();

con = new SqlConnection(path);

}

private void Form1_Load(object sender, EventArgs e)

{

// TODO: This line of code loads data into the 'eduDataSet1.lesson' table. You can move, or remove it, as needed.

this.lessonTableAdapter.Fill(this.eduDataSet1.lesson);

this.reportViewer1.RefreshReport();

this.reportViewer1.RefreshReport();

UpdateData();

}

private void label1_Click(object sender, EventArgs e)

{

}

private void button2_Click(object sender, EventArgs e)

{

con.Open();

SqlCommand cmd = con.CreateCommand();

cmd.CommandType = CommandType.Text;

cmd = new SqlCommand("insert into lesson (LID, LName, LCredit, LRel) values ('" + textBox1.Text + "','" + textBox2.Text + "','" + textBox3 + "','" + textBox4 + "')", con);

cmd.ExecuteReader();

con.Close();

textBox1.Text = "";

textBox2.Text = "";

textBox3.Text = "";

textBox4.Text = "";

UpdateData();

MessageBox.Show("????????? ?????????");

}

public void UpdateData()

{

}

private void label5_Click(object sender, EventArgs e)

{

}

private void button3_Click(object sender, EventArgs e)

{

try

{

if (textBox5.Text != "")

{

con.Open();

SqlCommand cmd = con.CreateCommand();

cmd.CommandType = CommandType.Text;

cmd.CommandText = "delete from lesson where LID = '" +

textBox5.Text + "'";

cmd.ExecuteNonQuery();

con.Close();

MessageBox.Show("????????? ??????????.");

}

else

{

MessageBox.Show("?? ?????? ?????? ????? ??????? ??!!!");

}

}

catch (Exception ex)

{

MessageBox.Show("?? ????? ???? ???????? ?????!!!");

}

UpdateData();

}

}

}