ObjectManager Class

Definition

Namespace:

System.Runtime.Serialization

Assembly:

System.Runtime.Serialization.Formatters.dll

Source:

ObjectManager.cs

Keeps track of objects as they are deserialized.

public ref class ObjectManager

public class ObjectManager

type ObjectManager = class

Public Class ObjectManager

Inheritance

Object

ObjectManager

Examples

The following code example shows how to use the ObjectManager class to walk through an object graph, traversing to each object only once.

using System;
using System.Text;
using System.Collections;
using System.Runtime.Serialization;
using System.Reflection;

// This class walks through all the objects once in an object graph.
public sealed class ObjectWalker : IEnumerable, IEnumerator {
   private Object m_current;

   // This stack contains the set of objects that will be enumerated.
   private Stack m_toWalk = new Stack();

   // The ObjectIDGenerator ensures that each object is enumerated just once.
   private ObjectIDGenerator m_idGen = new ObjectIDGenerator();

   // Construct an ObjectWalker passing the root of the object graph.
   public ObjectWalker(Object root) {
      Schedule(root);
   }

   // Return an enumerator so this class can be used with foreach.
   public IEnumerator GetEnumerator() {
      return this;
   }

   // Resetting the enumerator is not supported.
   public void Reset() {
      throw new NotSupportedException("Resetting the enumerator is not supported.");
   }

   // Return the enumeration's current object.
   public Object Current { get { return m_current; } }

   // Walk the reference of the passed-in object.
   private void Schedule(Object toSchedule) {
      if (toSchedule == null) return;

      // Ask the ObjectIDManager if this object has been examined before.
      Boolean firstOccurrence;
      m_idGen.GetId(toSchedule, out firstOccurrence);

      // If this object has been examined before, do not look at it again just return.
      if (!firstOccurrence) return;

      if (toSchedule.GetType().IsArray) {
         // The object is an array, schedule each element of the array to be looked at.
         foreach (Object item in ((Array)toSchedule)) Schedule(item);
      } else {
         // The object is not an array, schedule this object to be looked at.
         m_toWalk.Push(toSchedule);
      }
   }

   // Advance to the next item in the enumeration.
   public Boolean MoveNext() {
      // If there are no more items to enumerate, return false.
      if (m_toWalk.Count == 0) return false;

      // Check if the object is a terminal object (has no fields that refer to other objects).
      if (!IsTerminalObject(m_current = m_toWalk.Pop())) {
         // The object does have field, schedule the object's instance fields to be enumerated.
         foreach (FieldInfo fi in m_current.GetType().GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)) {
            Schedule(fi.GetValue(m_current));
         }
      }
      return true;
   }

   // Returns true if the object has no data fields with information of interest.
   private Boolean IsTerminalObject(Object data) {
      Type t = data.GetType();
      return t.IsPrimitive || t.IsEnum || t.IsPointer || data is String;
   }
}

public sealed class App {
   // Define some fields in the class to test the ObjectWalker.
   public String name = "Fred";
   public Int32 Age = 40;

   static void Main() {
      // Build an object graph using an array that refers to various objects.
      Object[] data = new Object[] { "Jeff", 123, 555L, (Byte) 35, new App() };

      // Construct an ObjectWalker and pass it the root of the object graph.
      ObjectWalker ow = new ObjectWalker(data);

      // Enumerate all of the objects in the graph and count the number of objects.
      Int64 num = 0;
      foreach (Object o in ow) {
         // Display each object's type and value as a string.
         Console.WriteLine("Object #{0}: Type={1}, Value's string={2}",
            num++, o.GetType(), o.ToString());
      }
   }
}

// This code produces the following output.
//
// Object #0: Type=App, Value's string=App
// Object #1: Type=System.Int32, Value's string=40
// Object #2: Type=System.String, Value's string=Fred
// Object #3: Type=System.Byte, Value's string=35
// Object #4: Type=System.Int64, Value's string=555
// Object #5: Type=System.Int32, Value's string=123
// Object #6: Type=System.String, Value's string=Jeff

Remarks

During deserialization, the Formatter queries the ObjectManager to determine whether a reference to an object in the serialized stream refers to an object that has already been deserialized (a backward reference), or to an object that has not yet been deserialized (a forward reference). If the reference in the serialized stream is a forward reference, then the Formatter can register a fixup with the ObjectManager. If the reference in the serialized stream is a backward reference, the Formatter immediately completes the reference. Fixup refers to the process of finalizing object references not already completed during the object deserialization process. After the required object has been deserialized, the ObjectManager will complete the reference.

The ObjectManager follows a set of rules that dictate the fixup order. All objects that implement ISerializable or have a ISerializationSurrogate can expect to have all the objects that they transmitted through SerializationInfo available when the object tree is deserialized. However, a parent object cannot presume that all its child objects will be fully completed when it is fully deserialized. All child objects will be present but not all the grandchild objects will necessarily be present. If an object needs to take certain actions that depend on executing code on its child objects, it can delay these actions, implement the IDeserializationCallback interface, and execute the code only when it is called back on this interface.

Constructors

ObjectManager(ISurrogateSelector, StreamingContext)

Initializes a new instance of the ObjectManager class.

Methods

DoFixups()	Performs all the recorded fixups.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetObject(Int64)	Returns the object with the specified object ID.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
RaiseDeserializationEvent()	Raises the deserialization event to any registered object that implements IDeserializationCallback.
RaiseOnDeserializingEvent(Object)	Invokes the method marked with the OnDeserializingAttribute.
RecordArrayElementFixup(Int64, Int32, Int64)	Records a fixup for one element in an array.
RecordArrayElementFixup(Int64, Int32[], Int64)	Records fixups for the specified elements in an array, to be executed later.
RecordDelayedFixup(Int64, String, Int64)	Records a fixup for an object member, to be executed later.
RecordFixup(Int64, MemberInfo, Int64)	Records a fixup for a member of an object, to be executed later.
RegisterObject(Object, Int64)	Registers an object as it is deserialized, associating it with objectID.
RegisterObject(Object, Int64, SerializationInfo)	Registers an object as it is deserialized, associating it with objectID, and recording the SerializationInfo used with it.
RegisterObject(Object, Int64, SerializationInfo, Int64, MemberInfo)	Registers a member of an object as it is deserialized, associating it with objectID, and recording the SerializationInfo.
RegisterObject(Object, Int64, SerializationInfo, Int64, MemberInfo, Int32[])	Registers a member of an array contained in an object while it is deserialized, associating it with objectID, and recording the SerializationInfo.
ToString()	Returns a string that represents the current object. (Inherited from Object)