ManagementObjectSearcher not found

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.Management;
using System.Collections.Generic;
using System.Management;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\WMI", "SELECT * FROM MSStorageDriver_ATAPISmartData");

//here ManagementObjectSearcher not found

                foreach (ManagementObject queryObj in searcher.Get())
                {
                    if (queryObj["VendorSpecific"] != null)
                    {
                        byte[] arrVendorSpecific = (byte[])(queryObj["VendorSpecific"]);
                        string temp = arrVendorSpecific[115].ToString();
                    }
                }
            }
            catch (Exception)
            {

                throw;
            }

        }
    }
}