How to use ManagementObjectSearcher?

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C#

.NET

I am using .net 2010
Now I am trying to get the user if from a process id. The code is:

using System;
using System.Net;
using System.Collections;
//using System.Net.NetworkInformation;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Management;
using System.Security.Permissions;
using System.Security.Principal;
using System.ComponentModel.Composition;
using System.ComponentModel;
using System.Diagnostics;


namespace getUser
{
    public static class Utils
    {
        public const int NO_ERROR = 0;
        public const int MIB_TCP_STATE_CLOSED = 1;
        public const int MIB_TCP_STATE_LISTEN = 2;
        public const int MIB_TCP_STATE_SYN_SENT = 3;
        public const int MIB_TCP_STATE_SYN_RCVD = 4;
        public const int MIB_TCP_STATE_ESTAB = 5;
        public const int MIB_TCP_STATE_FIN_WAIT1 = 6;
        public const int MIB_TCP_STATE_FIN_WAIT2 = 7;
        public const int MIB_TCP_STATE_CLOSE_WAIT = 8;
        public const int MIB_TCP_STATE_CLOSING = 9;
        public const int MIB_TCP_STATE_LAST_ACK = 10;
        public const int MIB_TCP_STATE_TIME_WAIT = 11;
        public const int MIB_TCP_STATE_DELETE_TCB = 12;
        //#region helper function
        const int MAXSIZE = 16384; // size _does_ matter
        public static string GetProcessInfoByPID(int PID, out string User, out string Domain)//, out string OwnerSID)
        {
            //DataTable dt = new DataTable();
            //dt.Columns.Add("ProcessID");
            //dt.Columns.Add("Name");
            //dt.Columns.Add("Description");
            //dt.Columns.Add("User");
            //dt.Columns.Add("Domain");
            //dt.Columns.Add("OwnerSID");
            User = String.Empty;
            Domain = String.Empty;
            String OwnerSID = String.Empty;
            string processname = String.Empty;
            try
            {
                ObjectQuery sq = new ObjectQuery("Select * from Win32_Process Where ProcessID = '" + PID + "'");
                //ObjectQuery sq = new ObjectQuery(Query);
                ManagementObjectSearcher searcher = new ManagementObjectSearcher(sq);
                if (searcher.Get().Count == 0)
                    return "Unknown";
                foreach (ManagementObject oReturn in searcher.Get())
                {
                    //Name of process
                    //arg to send with method invoke to return user and domain - below is link to SDK doc on it
                    string[] o = new String[2];
                    //Invoke the method and populate the o var with the user name and domain
                    oReturn.InvokeMethod("GetOwner", (object[])o);
                    //int pid = (int)oReturn["ProcessID"];
                    processname = (string)oReturn["Name"];
                    //dr[2] = oReturn["Description"];
                    User = o[0];
                    if (User == null)
                        User = String.Empty;
                    Domain = o[1];
                    if (Domain == null)
                        Domain = String.Empty;
                    string[] sid = new String[1];
                    oReturn.InvokeMethod("GetOwnerSid", (object[])sid);
                    OwnerSID = sid[0];
                    return OwnerSID;
                }
            }
            catch
            {
                return OwnerSID;
            }
            return OwnerSID;
        }
    }
}

Now I get this error:

Error	3	The type 'System.ComponentModel.Component' is defined in an assembly that is not referenced. You must add a reference to assembly 'System, Version=1.0.3300.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.	C:\Documents and Settings\Administrator\My Documents\Visual Studio 2010\Projects\getUser\getprocessownersid.cs	54	17	getUser

Can anyone tell me what to do?