Am having trouble with c# code can anyone help me

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.Data.SqlClient;

namespace WindowsFormsApplication9
{
    public partial class Form1 : Form
    {
        SqlConnection con;
        SqlCommand cmd;
        SqlDataReader dr;
        string SqlStr;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            con = new SqlConnection("Data Source=.\\SQLEXPRESS;Initial Catalog=employee;Integrated Security=True");
            
            //textBox1.Text = con.ConnectionString;
            con.Open();
            cmd = con.CreateCommand();
            cmd.CommandText = "Select Empno,Ename,Job,Salary From Emplye Order By Empno";
            dr = cmd.ExecuteReader();
            ShowData();

        }
        private void ShowData()
        {
            if (dr.Read())
            {
                textBox1.Text = dr[0].ToString();
                textBox2.Text = dr[1].ToString();
                textBox3.Text = dr[2].ToString();
                textBox3.Text = dr[3].ToString();
            }
            else   MessageBox.Show("No data exists.");
        }

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

        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text=textBox2.Text=textBox3.Text=textBox4.Text="";
            dr.Close();
            cmd.CommandText="select IsNULL(Max(Empno),1000)+1 From Emplye";
            textBox1.Text=cmd.ExecuteScalar().ToString();
            button3.Enabled = true;
            textBox2.Focus();
        }
        private void ExecuteDML()
        {
            DialogResult d = MessageBox.Show("Are you sure of executing the below Sql Statement?\n\n" + SqlStr, "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (d == DialogResult.Yes)
            {
                cmd.CommandText = SqlStr;
                int count = cmd.ExecuteNonQuery();
                if (count > 0) MessageBox.Show("Statement excuted successfully");
                else
                    MessageBox.Show("Statement failed execution");
                ShowData();
            }
        }
        private void button3_Click(object sender, EventArgs e)
        {
            SqlStr="Insert Emplye(Empno,Ename,Job,Salary)Values("+textBox1.Text+",'"+textBox2.Text+"'.'"+textBox3.Text+"',"+textBox4.Text+")";
            ExecuteDML();
            
        }

        private void button4_Click(object sender, EventArgs e)
        {
            SqlStr="Update Emplye Set Ename='"+textBox2.Text+"',Job='"+textBox3.Text+"',salary="+textBox4.Text+"where Empno+"+textBox1.Text;dr.Close();
            ExecuteDML();
        }

        private void button5_Click(object sender, EventArgs e)
        {
             SqlStr="Delete From Employe where Empno="+textBox1.Text;
             dr.Close();
             ExecuteDML();
        }

        private void button6_Click(object sender, EventArgs e)
        {
         if(con.State != ConnectionState.Closed)
         {
             con.Close();
         }
         this.Close();
        }
    }
}