C# การจะทำให้ datagridview refresh อย่างไรครับ Windows App ครับ

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 AoobShop
{
    public partial class Position : Form
    {
        private int setID;
        public Position()
        {
            InitializeComponent();
        }

        private void Position_Load(object sender, EventArgs e)
        {
            showGrid();
        }

        private void groupBox1_Enter(object sender, EventArgs e)
        {

        }

        private void button4_Click(object sender, EventArgs e)
        {
            Addposition addposition = new Addposition();
            addposition.Show();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            search.Visible = true;
            showGrid();
        }
        public void showGrid()
        {
            search.DataSource = null;
            search.Rows.Clear();
            search.Columns.Clear();

            DataGridViewLinkColumn link = new DataGridViewLinkColumn();
            link.UseColumnTextForLinkValue = true;
            link.HeaderText = "แก้ไข";
            link.DataPropertyName = "lnkColumn";
            //link.ActiveLinkColor = Color.White;
            link.LinkBehavior = LinkBehavior.SystemDefault;
            link.LinkColor = Color.Blue;
            link.Text = "แก้ไข";
            link.Width = 50;
            //link.VisitedLinkColor = Color.YellowGreen;
            search.Columns.Add(link);


            DataGridViewLinkColumn link1 = new DataGridViewLinkColumn();
            link1.UseColumnTextForLinkValue = true;
            link1.HeaderText = "ลบ";
            link1.DataPropertyName = "lnkColumn";
            //link.ActiveLinkColor = Color.White;
            link1.LinkBehavior = LinkBehavior.SystemDefault;
            link1.LinkColor = Color.Blue;
            link1.Text = "ลบ";
            link1.Width = 50;
            //link.VisitedLinkColor = Color.YellowGreen;
            search.Columns.Add(link1);

            string query = "SELECT POSITION_CODE, POSITION_NAME,POSITION_ID";
            query += " FROM Position";
            query += " where 1=1";

            if (!textid.Text.Equals(""))
            {
                query += "AND POSITION_CODE LIKE '%" + textid.Text + "%'";
            }

            if (!textname.Text.Equals(""))
            {
                query += "AND POSITION_NAME LIKE '%" + textname.Text + "%'";
            }

          

            ClassConnectDB conn = new ClassConnectDB();
            SqlDataReader drr;
            drr = conn.SelectSqlDataReader(query);
            DataTable dt = new DataTable();

            dt.Load(drr);

            search.DataSource = dt;

            search.Columns[2].HeaderText = "รหัสตำแหน่ง";
            search.Columns[3].HeaderText = "ชื่อตำแหน่ง";
            search.Columns[4].HeaderText = "รหัสตำแหน่ง";
            search.Columns[4].Visible = false;
            conn.Close();
            
        }

        private void search_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            setID = Convert.ToInt32(search.Rows[e.RowIndex].Cells[4].Value.ToString());
        }

        private void search_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 0)
            {
                /*
                 edit.editEmployee callemp = new edit.editEmployee();
                 callemp.Show();*/

                int row;
                row = e.RowIndex;
                if (!search.Rows[row].Cells[2].Value.ToString().Equals(""))
                {

                    // int code = Convert.ToInt32(gvSearch.Rows[row].Cells[2].Value.ToString());
                    //MessageBox.Show(search.Rows[row].Cells[2].Value.ToString());
                    string emp_code = search.Rows[row].Cells[2].Value.ToString();
                    edit.editPosition callemp = new edit.editPosition(emp_code);
                    callemp.Show();

                }
            }

            else if (e.ColumnIndex == 1)
            {
                if (MessageBox.Show("ต้องการลบข้อมูลใช่หรือไม่?", "ยืนยันการลบข้อมูล", MessageBoxButtons.YesNo) == DialogResult.Yes)
                {

                    try
                    {
                        string id = "";
                        string sqlidelete = "DELETE FROM Position where POSITION_ID=@id";
                        string Addvalue = "@id";
                        string value = setID.ToString();

                        ClassConnectDB conn = new ClassConnectDB();

                        bool re = conn.DeleteValue(sqlidelete, Addvalue, value);
                        if (re) { MessageBox.Show("ลบข้อมูลเรียบร้อยแล้ว"); }
                        else { MessageBox.Show("ไม่สามารถลบข้อมูลได้"); }
                        conn.Close();
                        showGrid();
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show("ERROR : " + ex.ToString());
                    }
                }
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            search.Visible = false;
            textid.Text = "";
            textname.Text = "";
        }
    }
}

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 AoobShop
{
    public partial class Addposition : Form
    {
        public Addposition()
        {
            InitializeComponent();
        }
        public void addnumber()
        {
            try
            {
                ClassConnectDB conn = new ClassConnectDB();
                string sqlcount = "SELECT COUNT(*) FROM Position";
                SqlDataReader dr;
                DataTable dt;
                dr = conn.SelectSqlDataReader(sqlcount);
                if (dr.HasRows)
                {
                    dt = new DataTable();
                    dt.Load(dr);
                    int number = Convert.ToInt32(dt.Rows[0][0].ToString());
                    number += 1;
                    if (number >= 100)
                    {
                        textpositionid.Text = "PO" + number;
                    }
                    else if (number >= 10)
                    {
                        textpositionid.Text = "PO0" + number;
                    }
                    else
                        textpositionid.Text = "PO00" + number;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.StackTrace);
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (MessageBox.Show("ต้องการเพิ่มข้อมูลใช่หรือไม่?", "ยืนยันการเพิ่มข้อมูล", MessageBoxButtons.YesNo) == DialogResult.Yes)
            {

                try
                {
                    string name = textname.Text;
                    string code = textpositionid.Text;
                    string sqlinsert = @"INSERT INTO Position (POSITION_NAME,POSITION_CODE)
                               VALUES(@name,@code)";
                    string Addvalue = "@name,@code";
                    string value = name + "," + code;

                    ClassConnectDB conn = new ClassConnectDB();
                    bool re = conn.InsertValue(sqlinsert, Addvalue, value);

                    if (re) { MessageBox.Show("บันทึกข้อมูลเรียบร้อยแล้ว"); }
                    else { MessageBox.Show("ไม่สามารถบันทึกข้อมูลได้"); }
                    conn.Close();
                    this.Close();
                    Position callposition = new Position();
                    callposition.showGrid();
                }
                catch (Exception ex)
                {
                    MessageBox.Show("ERROR : " + ex.ToString());
                }
            }
        }

        private void Addposition_Load(object sender, EventArgs e)
        {
            textpositionid.Enabled = false;
            addnumber();
        }

      
    }
}