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Demonstrating Serialization

The first process that I will illustrate involves exporting an instance of the Domain class to an XML document using the Serialize method of XmlSerializer. Serialize has a variety of method overloads to handle different I/O objects: Stream, TextWriter, and XmlWriter. The easiest way to deal with file I/O is to use the StreamWriter; it provides a TextWriter-compatible interface on top of the file system.

Before we can serialize, we have to create security object hierarchy that provides us with sufficient content for educational value by executing our CreateDomain method. After object creation, we pass the class type, a reference to our top-level Domain object, and the filename as parameters to the ExportDomain method in Listing 2. It relays the parameters to the Serialize method of the XmlSerializer creating the XML document in Listing 3.

Listing 2: Code for Export and Import of Domain Class via XML

using System;
using System.IO;
using System.Xml.Serialization;

namespace Serialize
{
    class SerializeMain
    {
        static void Main(string[] args)
        {
            // call routine that constructs our
            // tree of domain objects
            Domain expdomain = CreateDomain();
            ExportDomain(typeof(Domain),
                expdomain,"C:\\Domain.xml");

            // call routine that retrieves a
            // tree of domain objects from disk
            // and returns us an object reference
            Domain impdomain = ImportDomain(typeof(Domain),
                "C:\\Domain.xml");
            DisplayDomain(impdomain);
        }


        static string GetNewGUIDString()
        {

            // create a GUID
            return Guid.NewGuid().ToString();
        }



        static void ExportDomain(System.Type type, Object o,
                            string filename)
        {

            // create the serializer
            XmlSerializer serializer = new XmlSerializer(type);

            // set up the serialize to write its output to
            // to a streamwriter that is pointing at a file
            StreamWriter writer = new StreamWriter(filename);

            // serialize the object to disk
            serializer.Serialize(writer,o);

            // close the writer to release the file resource
            writer.Close();
        }

        static Domain ImportDomain(System.Type type,
                            string filename)
        {
            // create the serializer
            XmlSerializer serializer = new XmlSerializer(type);

            // create a streamreader that reads from the
            // input file
            StreamReader reader = new StreamReader(filename);

            // instruct serializer to deserialize an object
            // reference form the file and cast it to the
            // appropriate reference type
            Domain newdomain = (Domain)
                serializer.Deserialize(reader);

            // close the reader to release the file resource
            reader.Close();

            // return our newly minted object
            return newdomain;
        }

        static Domain CreateDomain()
        {
            Domain domain = new Domain();
            domain.ID = GetNewGUIDString();
            domain.Name = "InformIT";

            User[] users = new User[3];
            users[0] = new User();
            users[0].ID = GetNewGUIDString();
            users[0].Name = "Dale Michalk";
            users[0].Password = "password";

            users[1] = new User();
            users[1].ID = GetNewGUIDString();
            users[1].Name = "Joe User";
            users[1].Password = "password";

            users[2] = new User();
            users[2].ID = GetNewGUIDString();
            users[2].Name = "Guest User";
            users[2].Password = "password";

            Group[] groups = new Group[3];
            groups[0] = new Group();
            groups[0].ID = GetNewGUIDString();
            groups[0].Name = "Admins";
            groups[0].Users = new UserRef[1];
            groups[0].Users[0] = new UserRef();
            groups[0].Users[0].ID = users[0].ID;

            groups[1] = new Group();
            groups[1].ID = GetNewGUIDString();
            groups[1].Name = "Users";
            groups[1].Users = new UserRef[2];
            groups[1].Users[0] = new UserRef();
            groups[1].Users[0].ID = users[0].ID;
            groups[1].Users[1] = new UserRef();
            groups[1].Users[1].ID = users[1].ID;

            groups[2] = new Group();
            groups[2].ID = GetNewGUIDString();
            groups[2].Name = "Guests";
            groups[2].Users = new UserRef[1];
            groups[2].Users[0] = new UserRef();
            groups[2].Users[0].ID = users[2].ID;

            domain.Users = users;
            domain.Groups = groups;

            return domain;

        }

        static void DisplayDomain(Domain domain)
        {
            // Domain
            Console.WriteLine("Domain: {0}",domain.Name);
            Console.WriteLine("\tID:{0}",domain.ID);
            // Users
            Console.WriteLine("");
            Console.WriteLine("Users");
            foreach (User user in domain.Users)
            {
                Console.WriteLine("\tName:{0}",user.Name);
                Console.WriteLine("\t\tID:{0}",user.ID);
                Console.WriteLine("\t\tPassword:{0}",
                    user.Password);
            }
            // Groups
            Console.WriteLine("");
            Console.WriteLine("Groups");
            foreach (Group group in domain.Groups)
            {
                Console.WriteLine("\tName:{0}",group.Name);
                Console.WriteLine("\t\tID:{0}",group.ID);
                Console.WriteLine("\t\tUsers:");
                foreach (UserRef userref in group.Users)
                {
                    Console.WriteLine("\t\t\t{0}",
                        ,userref.ID);
                }
                Console.WriteLine("");
            }
        }

    }
}

Listing 3: XML Document Result from ExportDomain

<?xml version="1.0" encoding="utf-8"?>
<Domain xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:xsd="http://www.w3.org/2001/XMLSchema">
 <ID>2ca519b2-a558-4b7b-b243-408588ba629a</ID>
 <Name>InformIT</Name>
 <Users>
  <User>
   <ID>03ae3f5a-e46d-4fcf-bc33-fdaeee22dcc0</ID>
   <Name>Dale Michalk</Name>
   <Password>password</Password>
  </User>
  <User>
   <ID>2831d8af-55aa-4f7c-b212-c87e7fc1eea2</ID>
   <Name>Joe User</Name>
   <Password>password</Password>
  </User>
  <User>
   <ID>0c5864a6-b37d-4424-b57e-3a2b86f0e183</ID>
   <Name>Guest User</Name>
   <Password>password</Password>
  </User>
 </Users>
 <Groups>
  <Group>
   <ID>91d08bbd-8838-4413-8dcf-c63fb02848e0</ID>
   <Name>Admins</Name>
   <Users>
    <UserRef>
     <ID>03ae3f5a-e46d-4fcf-bc33-fdaeee22dcc0</ID>
    </UserRef>
   </Users>
  </Group>
  <Group>
   <ID>b36c1cfb-7de1-4ac9-8f21-9de7ab3cf76d</ID>
   <Name>Users</Name>
   <Users>
    <UserRef>
     <ID>03ae3f5a-e46d-4fcf-bc33-fdaeee22dcc0</ID>
    </UserRef>
    <UserRef>
     <ID>2831d8af-55aa-4f7c-b212-c87e7fc1eea2</ID>
    </UserRef>
   </Users>
  </Group>
  <Group>
   <ID>db3efa55-f228-435c-9833-e62f7dca4078</ID>
   <Name>Guests</Name>
   <Users>
    <UserRef>
     <ID>0c5864a6-b37d-4424-b57e-3a2b86f0e183</ID>
    </UserRef>
   </Users>
  </Group>
 </Groups>
</Domain>

To rehydrate an object from an existing XML store, we use the DeSerialize method of the XmlSerializer. It is overloaded to take a variety of input sources: Stream, TextReader, or XmlReader. In the ImportDomain method, the example uses the StreamReader to pull the XML document from disk and provide a TextReader-compatible source. To verify the process, the code calls on the DisplayDomain method to spit out information to the console. The data in the document and object instance report in Listing 4 should be the same if the process is working properly.

Listing 4: DisplayDomain Console Output

Domain: InformIT
    ID:830651e9-b7e7-4c81-9a99-34cc7f583264

Users
    Name:Dale Michalk
        ID:99a13f10-9317-41d2-9370-62581371a49f
        Password:password
    Name:Joe User
        ID:3d3cc57d-5a19-491a-be4e-e2bee5e4bdd7
        Password:password
    Name:Guest User
        ID:2d113809-d77f-427a-b5c9-17641b2a8467
        Password:password

Groups
    Name:Admins
        ID:85317acc-8991-47e7-af0b-3d97bf45aab4
        Users:
            99a13f10-9317-41d2-9370-62581371a49f

    Name:Users
        ID:2bb3ccc7-d386-41cf-b480-c8c1e9860aa2
        Users:
            99a13f10-9317-41d2-9370-62581371a49f
            3d3cc57d-5a19-491a-be4e-e2bee5e4bdd7

    Name:Guests
        ID:d119d679-f4fc-4ba2-b3d2-52f2146965c9
        Users:
            2d113809-d77f-427a-b5c9-17641b2a8467
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