Simple Insert, Update, Delete, Retrieve Opertions in C# Windows Form Application

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;

using System.Data.SqlClient;             //namespace for using sqlserver components



namespace InsertApp
{
    public partial class Form1 : Form
    {

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Getgrid();
        }

        public void Getgrid()
        {
            SqlConnection con = new SqlConnection("Data Source=SQLEXPRESS; Initial Catalog=SQLDATABASE; Integrated Security=SSPI ");
            con.Open();
            SqlDataAdapter da = new SqlDataAdapter("select * from employee", con);
            DataSet ds = new DataSet();
            da.Fill(ds);
            dataGridView1.DataSource = ds.Tables[0];
            con.Close();
        }

        // Method for Insert the values
        private void btnInsert_Click(object sender, EventArgs e)
        {
            SqlConnection con=new SqlConnection("Data Source=SQLEXPRESS; Initial Catalog=SQLDATABASE; Integrated Security=SSPI ");
            con.Open();

                SqlCommand cmd = new SqlCommand("Insert into employee values('" + txtId.Text + "','" + txtName.Text + "','" + txtDesigid.Text + "','" + txtEmploc.Text + "')", con);
                int check = cmd.ExecuteNonQuery();
                if (check > 0)
                {
                    MessageBox.Show("Inserted");
                }
                else
                {
                    MessageBox.Show("Not- Inserted");
                }
                cmd.Dispose();
                con.Close();
                Getgrid();

        }

        // Method for Update the values
        private void btnUpdate_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("Data Source=SQLEXPRESS; Initial Catalog=SQLDATABASE; Integrated Security=SSPI ");
            con.Open();

                SqlCommand cmd = new SqlCommand("update employee set emp_id='" + txtId.Text + "', emp_name='" + txtName.Text + "',desig_id='" + txtDesigid.Text + "',emp_location='" + txtEmploc.Text + "' where emp_id='"+txtId.Text+"'", con);
                cmd.ExecuteNonQuery();
                MessageBox.Show("updated");
                cmd.Dispose();
                con.Close();
                Getgrid();
        }

        // Method for Delete the values
        private void btnDelete_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("Data Source=SQLEXPRESS; Initial Catalog=SQLDATABASE; Integrated Security=SSPI ");
            con.Open();

            SqlCommand cmd = new SqlCommand("delete from employee where emp_id='" + txtId.Text + "'", con);
            cmd.ExecuteNonQuery();
            MessageBox.Show("deleted");
            cmd.Dispose();
            con.Close();
            Getgrid();
        }

        // Method for Retrieve the values
        private void btnRetrieve_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("Data Source=SQLEXPRESS; Initial Catalog=SQLDATABASE; Integrated Security=SSPI ");
            con.Open();

            SqlCommand cmd = new SqlCommand("select * from employee where emp_id='" + txtId.Text + "'", con);
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                txtId.Text = dr[0].ToString();
                txtName.Text = dr[1].ToString();
                txtDesigid.Text = dr[2].ToString();
                txtEmploc.Text = dr[3].ToString();
            }
        }

        // Method for Clear values in textbox
        private void btnClear_Click(object sender, EventArgs e)
        {
            clearmethod();             // calling clear method
        }

        public void clearmethod()
        {
            txtId.Text = "";
            txtName.Text = "";
            txtDesigid.Text = "";
            txtEmploc.Text = "";
        }
    }
}