cruid command through by . windows .net

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;
using System.Data;


namespace WindowsFORMCONNECTION
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
        try
{
//create  object  of Connection Class..................
SqlConnection con = new SqlConnection();
//Set Connection String property of Connection object..................
con.ConnectionString = @"Data Source=KING_OF_JAUNPUR\SQLEXPRESS;Initial Catalog=SqlPractice;User ID=sa;Password=123";
//Open Connection..................
con.Open();
//Create object of Command Class................
SqlCommand cmd = new SqlCommand();
//set Connection Property  of  Command object.............
cmd.Connection = con;
//Set Command type of command object
//1.StoredProcedure
//2.TableDirect
//3.Text   (By Default)
cmd.CommandType = CommandType.Text;
//Set Command text Property of command object.........
cmd.CommandText = "insert into Customer(SrNo,FirstName,LastName,Dob) values(" + Convert.ToInt32(textBox1.Text) + ",'" +textBox2.Text+ "','" + textBox3.Text + "','" +Convert.ToDateTime(textBox4.Text).ToShortDateString() + "')";

//Execute command by calling following method................
 //  1.ExecuteNonQuery()
 //      It  query using for  insert,delete,update command...........
 //2.ExecuteScalar()
 //    It  query return a single value and insert all record...................(using select,insert command)
//   3.ExecuteReader()
//      It  query return one or more than one record....................................

cmd.ExecuteNonQuery();


MessageBox.Show("Data Saved");
//TextBoxClear();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}


        }

        private void button2_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = "Data Source=KING_OF_JAUNPUR\\SQLEXPRESS;Initial Catalog=SqlPractice;User ID=sa;Password=123";
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "select * from Customer where SrNo='" + Convert.ToInt32(textBox1.Text) + "'";
            cmd.Connection = con;
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {

                textBox2.Text = dr["FirstName"].ToString();
                textBox3.Text = dr[2].ToString();
                textBox4.Text = dr.GetDateTime(3).ToShortDateString();
            }
            else
                MessageBox.Show("Record not found", "No record", MessageBoxButtons.OK, MessageBoxIcon.Information);
            con.Close();


        }

        private void button3_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = "Data Source=KING_OF_JAUNPUR\\SQLEXPRESS;Initial Catalog=SqlPractice;User ID=sa;Password=123";
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "Delete from Customer where SrNo='" + Convert.ToInt32(textBox1.Text) + "'";
            cmd.Connection = con;
            int i = cmd.ExecuteNonQuery();
            if (i > 0)
            {
                MessageBox.Show("Data delete Successfully for SrNo" + textBox1.Text);
              //  TextBoxClear();
            }
            else
            {
                MessageBox.Show("Record not found", "No record", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            con.Close();
        }

        private void button4_Click(object sender, EventArgs e)
        {
           SqlConnection con = new SqlConnection();
           con.ConnectionString = "Data Source=KING_OF_JAUNPUR\\SQLEXPRESS;Initial Catalog=SqlPractice;User ID=sa;Password=123;";
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "Update Customer set  FirstName='" + textBox2.Text + "',LastName='" + textBox3.Text  + "',Dob='" +Convert.ToDateTime(textBox4.Text ) + "' where SrNo='"+Convert.ToInt32(textBox1.Text )+"'";
cmd.Connection = con;
int i = cmd.ExecuteNonQuery();
if (i > 0)
{
MessageBox.Show("Data updated Successfully for SrNo" +textBox1.Text );
//TextBoxClear();
}
else
{
MessageBox.Show("Record not found", "No record", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
con.Close();
}
        }
    }