public class BackupRestoreUsers
{
    private List<string> usernames;

    public BackupRestoreUsers()
    {
    }

    public static void Main(string[] args)
    {
        BackupRestoreUsers test = new BackupRestoreUsers();
        test.usernames=test.GetUsers();
        foreach (string name in test.usernames)
        {
            Console.WriteLine(name);
            test.BackupUser(name);
        }
        Console.Read();
    }

    public List<string> GetUsers()
    {
        int EntriesRead;
        int TotalEntries;
        int Resume;
        IntPtr bufPtr;
        List<string> users = new List<string>();

        NetworkAPI.NetUserEnum(null, 0, 2, out bufPtr, -1, out EntriesRead, out TotalEntries, out Resume);
        if (EntriesRead > 0)
        {
            NetworkAPI.USER_INFO_0[] Users = new NetworkAPI.USER_INFO_0[EntriesRead];
            IntPtr iter = bufPtr;
            for (int i = 0; i < EntriesRead; i++)
            {
                Users[i] = (NetworkAPI.USER_INFO_0)Marshal.PtrToStructure(iter, typeof(NetworkAPI.USER_INFO_0));
                iter = (IntPtr)((int)iter + Marshal.SizeOf(typeof(NetworkAPI.USER_INFO_0)));
                users.Add(Users[i].usri0_name);
            }
            NetworkAPI.NetApiBufferFree(bufPtr);
        }
        return users;
    }

    public bool BackupUser(string username)
    {
        const int levelOfInfo=4;
        IntPtr bufPtr;

        NetworkAPI.NetUserGetInfo(null, username, levelOfInfo, out bufPtr);
        NetworkAPI.USER_INFO_4 userDetails = (NetworkAPI.USER_INFO_4)Marshal.PtrToStructure(bufPtr, typeof(NetworkAPI.USER_INFO_4));
        Console.WriteLine(userDetails.usri4_full_name);
        Console.WriteLine(userDetails.usri4_country_code);
        Console.WriteLine(userDetails.usri4_code_page);
        Console.WriteLine(userDetails.usri4_auth_flags);
        Console.WriteLine(userDetails.usri4_home_dir_drive);
        Console.WriteLine();
        NetworkAPI.NetApiBufferFree(bufPtr);
        return true;
    }
}

public class NetworkAPI
{
    // USER_INFO_0 - Structure to hold Just Usernames
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct USER_INFO_0
    {
        public String usri0_name;
    }

    // USER_INFO_3 - structure to hold detailed information of user
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct USER_INFO_4
    {
        public string usri4_name;
        public string usri4_password;
        public int usri4_password_age;
        public int usri4_priv;
        public string usri4_home_dir;
        public string usri4_comment;
        public int usri4_flags;
        public string usri4_script_path;
        public int usri4_auth_flags;
        public string usri4_full_name;
        public string usri4_usr_comment;
        public string usri4_parms;
        public string usri4_workstations;
        public int usri4_last_logon;
        public int usri4_last_logoff;
        public int usri4_acct_expires;
        public int usri4_max_storage;
        public int usri4_units_per_week;
        public IntPtr usri4_logon_hours;// PBYTE i.e. byte pointer converts to IntPtr
        public int usri4_bad_pw_count;
        public int usri4_num_logons;
        public string usri4_logon_server;
        public int usri4_country_code;
        public int usri4_code_page;
        public IntPtr usri4_user_sid;// PSID- Pointer to the Security IDentifier structure used to uniqly identify users or groups, generally ignored
        public int usri4_primary_group_id;
        public string usri4_profile;
        public string usri4_home_dir_drive;
        public int usri4_password_expired;
    }

    // NetUserAdd - To Add Users to a local machine or Network
    [DllImport("Netapi32.dll")]
    public extern static int NetUserAdd([MarshalAs(UnmanagedType.LPWStr)] string servername, int level, ref USER_INFO_4 buf, int parm_err);

    // NetUserDel - To delete Users from a local machine or Network
    [DllImport("Netapi32.dll")]
    public extern static int NetUserDel([MarshalAs(UnmanagedType.LPWStr)] string servername, [MarshalAs(UnmanagedType.LPWStr)] string username);

    // NetUserGetInfo - Returns to a struct Information about the specified user
    [DllImport("Netapi32.dll")]
    public extern static int NetUserGetInfo([MarshalAs(UnmanagedType.LPWStr)] string servername, [MarshalAs(UnmanagedType.LPWStr)] string username, int level, out IntPtr bufptr);

    // NetUserSetInfo - Allows us to modify User information
    [DllImport("Netapi32.dll")]
    public extern static int NetUserSetInfo([MarshalAs(UnmanagedType.LPWStr)] string servername, [MarshalAs(UnmanagedType.LPWStr)] string username, int level, ref USER_INFO_4 buf, int error);

    // NetUserChangePassword - Allows us to change a users password providing we have it
    [DllImport("Netapi32.dll")]
    public extern static int NetUserChangePassword([MarshalAs(UnmanagedType.LPWStr)] string domainname, [MarshalAs(UnmanagedType.LPWStr)] string username, [MarshalAs(UnmanagedType.LPWStr)] string oldpassword, [MarshalAs(UnmanagedType.LPWStr)] string newpassword);

    // NetUserEnum - Obtains a list of all users on local machine or network
    [DllImport("Netapi32.dll")]
    public extern static int NetUserEnum(string servername, int level, int filter, out IntPtr bufptr, int prefmaxlen, out int entriesread, out int totalentries, out int resume_handle);

    // NetAPIBufferFree - Used to clear the Network buffer after NetUserEnum
    [DllImport("Netapi32.dll")]
    public extern static int NetApiBufferFree(IntPtr Buffer);
}