C# Problem

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.Runtime.InteropServices;
using System.Management;
using System.Xml;
using System.Xml.Schema;
using Microsoft.SqlServer.Management.Smo;
using Microsoft.SqlServer.Management.Common;
using System.Data.SqlTypes;
using System.Data.SqlClient;
using System.Threading;

namespace Image_Tool
{
    public partial class Form1 : Form
    {
        string newpcname = "";
        string oldpcname = "";
        public Form1()
        {
            InitializeComponent();
            textBoxOldPCNavn.Text = Environment.MachineName;
            oldpcname = Environment.MachineName;
        }

        public void buttonDomain_Click(object sender, EventArgs e)
        {
            newpcname = textBoxPCNavn.Text + "PC";
            HandleJoinandRenameDomain("domain.local", newpcname, domainUser.Text, domainPassword.Text);
        }

        public string GetComputerName()
        {
            string szRet = "";
            ManagementClass objMC;
            ManagementObjectCollection objMOC;

            try
            {
                // caller doesn't have to catch
                objMC = new ManagementClass("Win32_ComputerSystem");
                objMOC = objMC.GetInstances();
            }
            catch (Exception e)
            {
                textBoxOutput.AppendText(e.Message);
                return szRet;
            }

            foreach (ManagementObject objMO in objMOC)
            {
                if (null != objMO)
                {
                    szRet = objMO["Name"].ToString();
                    break;
                }
            }

            return szRet;
        }

        public string GetDomainName()
        {
            string szRet = "";
            ManagementClass objMC;
            ManagementObjectCollection objMOC;

            try
            {
                // caller does not have to catch
                objMC = new ManagementClass("Win32_ComputerSystem");
                objMOC = objMC.GetInstances();
            }
            catch (Exception e)
            {
                textBoxOutput.AppendText(e.Message);
                return szRet;
            }

            foreach (ManagementObject objMO in objMOC)
            {
                if (null != objMO)
                {
                    if ((bool)objMO["partofdomain"])
                    {
                        szRet = objMO["domain"].ToString();
                        textBoxOutput.AppendText("Computeren er med i domænet: " + szRet + Environment.NewLine);
                    }
                    else
                    {
                        textBoxOutput.AppendText("Computeren er i en Workgroup, ikke domæne." + Environment.NewLine);
                    }
                }
            }

            return szRet;
        }

        public void HandleJoinandRenameDomain(string szDomain, string szNewHostname, string szUsername, string szPassword)
        {
            string szCurrentHostname = GetComputerName();
            string szCurrent = GetDomainName();
            ManagementObject objMO = new ManagementObject("Win32_ComputerSystem.Name='" + szCurrentHostname + "'");
            if (null != objMO)
            {
                ManagementBaseObject result;

                objMO.Scope.Options.EnablePrivileges = true;
                objMO.Scope.Options.Authentication = AuthenticationLevel.PacketPrivacy;
                objMO.Scope.Options.Impersonation = ImpersonationLevel.Impersonate;

                if ((szCurrentHostname.ToUpper() != szNewHostname.ToUpper()) && ("" != szNewHostname))
                {
                    try
                    {
                        textBoxOutput.AppendText("Join domæne: Sætter computernavn til " + szNewHostname.ToUpper() + Environment.NewLine);
                        ManagementBaseObject query2;
                        query2 = objMO.GetMethodParameters("Rename");
                        query2["Name"] = szNewHostname;
                        query2["Password"] = null;
                        query2["UserName"] = null;

                        result = objMO.InvokeMethod("Rename", query2, null);

                        if (0 != (uint)result["ReturnValue"])
                        {
                            textBoxOutput.AppendText("Kunne ikke ændre computernavnet, fejlkode: " + result["ReturnValue"].ToString() + Environment.NewLine);
                        }

                        textBoxOutput.AppendText("Success!" + Environment.NewLine);

                    }
                    catch (InvalidOperationException e)
                    {
                        textBoxOutput.AppendText("Join domæne fejlede: " + e.Message + Environment.NewLine);
                        return;
                    }
                    catch (ManagementException e)
                    {
                        textBoxOutput.AppendText("Join domæne fejlede, kunne ikke ændre computernavnet: " + e.Message + Environment.NewLine);
                        return;
                    }
                }
                Thread.Sleep(45000);
                if ("" != szCurrent)
                {
                    if (szCurrent.ToUpper() == szDomain.ToUpper())
                    {
                        textBoxOutput.AppendText("Denne computer er allerede på domænet: " + szCurrentHostname + szCurrent + Environment.NewLine);
                        return;

                    }
                    else
                    {
                        textBoxOutput.AppendText("Denne computer er allerede på et andet domain: " + szCurrent + Environment.NewLine);
                        return;
                    }
                }

                ManagementBaseObject query;
                try
                {
                    query = objMO.GetMethodParameters("JoinDomainOrWorkgroup");
                }
                catch (ManagementException)
                {
                    textBoxOutput.AppendText("Join domæne fejlede, kunne ikke finde den lokale computer (???)." + Environment.NewLine);
                    return;
                }
                query["Name"] = szDomain;
                query["Password"] = szPassword;
                query["UserName"] = szUsername;
                query["FJoinOptions"] = 3; // + 256 (tried with and with 256

                textBoxOutput.AppendText("Prøver WMI metoden JoinDomainOrWorkgroup." + Environment.NewLine + "Domæne: " + query["Name"].ToString() + Environment.NewLine + "Username: " + query["UserName"].ToString() + Environment.NewLine + "Join options: " + query["FJoinOptions"].ToString() + Environment.NewLine);
                try
                {
                    result = objMO.InvokeMethod("JoinDomainOrWorkgroup", query, null);
                }
                catch (ManagementException e)
                {
                    textBoxOutput.AppendText("Join domæne fejlede, kode: " + (uint)e.ErrorCode + " kunne ikke udføre forespørgslen: " + e.Message + Environment.NewLine);
                    return;
                }

                if (0 != (uint)result["ReturnValue"])
                {
                    textBoxOutput.AppendText("Join domæne fejlede: " + (uint)result["ReturnValue"] + " kunne ikke udføre forespørgslen." + Environment.NewLine);
                    return;
                }


            }
            else
            {
                textBoxOutput.AppendText("Join domæne fejlede: Kunne ikke åbne management objektet." + Environment.NewLine);
                return;
            }
        }


    }
}