Number will Increment by code in C#

Here ITEM_CODE will auto increment

//Code for Add & Save button of shown form
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace SALE_INVENTORY
{
    public partial class PRODUCTS : Form
    {
        SqlConnection con = new SqlConnection();
        DataTable dt;
        DataRow dr;
        String code;   

        public PRODUCTS()
        {
            InitializeComponent();


        private void PRODUCTS_Load(object sender, EventArgs e)
        {

            btnSave.Enabled = false;
            btnCancel.Enabled = false;
            btnUpdate.Enabled = false;

            cmbItemcode.Enabled = false;
            cmbItemName.Enabled = false;
            txtMP.Enabled = false;
            txtSP.Enabled = false;
            txtRem.Enabled = false;


            // TODO: This line of code loads data into the 's_productsDS.PRODUCTS_TABLE' table. You can move, or remove it, as needed.
            this.pRODUCTS_TABLETableAdapter.Fill(this.s_productsDS.PRODUCTS_TABLE);
        
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            try
            {
                btnEdit.Enabled = false;

                cmbItemcode.Enabled = true;
                cmbItemName.Enabled = true;
                txtMP.Enabled = true;
                txtSP.Enabled = true;
                txtRem.Enabled = true;

                btnEdit.Enabled = false;

                cmbItemcode.Text = "";
                cmbItemName.Text = "";
                txtMP.Text = "";
                txtSP.Text = "";
                txtRem.Text = "";

                int ctr, len;
                String prod_codeval;
                dt = s_productsDS.Tables["PRODUCTS_TABLE"];

                len = dt.Rows.Count - 1;
                dr = dt.Rows[len];
                code = dr["ITEM_CODE"].ToString();
                prod_codeval = code.Substring(2, 4);
                ctr = Convert.ToInt32(prod_codeval);

                if ((ctr >= 1) && (ctr < 9))
                {
                    ctr = ctr + 1;
                    cmbItemcode.Text= "IM000" + ctr;
                    
                }
                else if ((ctr >= 9) && (ctr < 99))
                {
                    ctr = ctr + 1;
                    cmbItemcode.Text = "IM00" + ctr;
                }
                else if ((ctr >= 99) && (ctr < 999))
                {
                    ctr = ctr + 1;
                    cmbItemcode.Text = "IM0" + ctr;
                }
                else if ((ctr >= 999) && (ctr < 9999))
                {
                    ctr = ctr + 1;
                    cmbItemcode.Text = "IM" + ctr;
                }
                                
                btnAdd.Enabled = false;
                btnSave.Enabled = true;
                btnCancel.Enabled = true;
                btnUpdate.Enabled = false;
            }
            catch
            {
                MessageBox.Show("There are Error");
            }
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
        

            try
            {
                dt = s_productsDS.Tables["PRODUCTS_TABLE"];
                dr = dt.NewRow();

                dr[0] = cmbItemcode.Text;
                dr[1] = cmbItemName.Text;
                dr[2] = txtMP.Text;
                dr[3] = txtSP.Text;
                dr[4] = txtRem.Text;
            
                dt.Rows.Add(dr);
                pRODUCTS_TABLETableAdapter.Update(s_productsDS.PRODUCTS_TABLE);
            
                MessageBox.Show("Record Save Successfuly", "Data Entry Operator", MessageBoxButtons.OK, MessageBoxIcon.Information);

                cmbItemcode.Enabled = false;
                cmbItemName.Enabled = false;
                txtMP.Enabled = false;
                txtSP.Enabled = false;
                txtRem.Enabled = false;


                btnAdd.Enabled = true;
                btnSave.Enabled = false;
                btnCancel.Enabled = false;
                btnEdit.Enabled = true;
                btnUpdate.Enabled = false;

            }
            catch
            {
                MessageBox.Show("Entered Data is not valid. Please enter valid data", "Data Entry Operator", MessageBoxButtons.OKCancel, MessageBoxIcon.Question);
            }

        }

    }
}

Before running this code you will need SQL Server 2005 table 'PRODUCTS_TABLE'.