Import function

       [ DllImport("user32") ]

       public static extern bool ExitWindowsEx(uint uFlags, uint dwReserved ) ;

Logon

       public bool Logon(string UserName,string Password)

       {                  

              //init variable

              string[] saTemp;

              string strUserName;

              string strDomainName;               

              RegistryKey rkTemp;                         

              try

              {    

                     //get user name and domain name

                     saTemp=UserName.Split("\".ToCharArray());                         

                     if(saTemp.Length>1)

                     {

                            strUserName=saTemp[1];

                            strDomainName=saTemp[0];

                     }

                     else

                     {

                            strUserName=saTemp[0];

                            strDomainName="";                                  

                     }

                     //write logon information to registry                                

                     rkTemp=Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon",true);           

                     rkTemp.SetValue("AutoAdminLogon","1");

                     rkTemp.SetValue("AutoLogonCount",1);

                     rkTemp.SetValue("DefaultUserName",strUserName);

                     rkTemp.SetValue("DefaultPassword",Password);

                     rkTemp.SetValue("DefaultDomainName",strDomainName);

                     rkTemp.Close();                  

                     //reboot

                     Reboot("");

                     return true;

              }

              catch(Exception exp)

              {

                     throw exp;

              }           

       }

LogOff

       ExitWindowsEx((uint)EWX.EWX_LOGOFF,0);

Reboot

       ExitWindowsEx((uint)(EWX.EWX_REBOOT | EWX.EWX_FORCE),0);

ShutDown

       ExitWindowsEx((uint)(EWX.EWX_SHUTDOWN | EWX.EWX_FORCE),0);