Type: System.Xml.Serialization.XmlSerializer

System.Xml.Serialization.XmlSerializer Class

Assembly: System.Xml.dll
Namespace: System.Xml.Serialization

Summary: Serializes and deserializes objects into and from XML documents. The XmlSerializer enables you to control how objects are encoded into XML.

C# Syntax:


        public class XmlSerializer

Remarks

XML serialization is the process of converting an object's public properties and fields to a serial format (in this case, XML) for storage or transport. Deserialization re-creates the object in its original state from the XML output. You can thus think of serialization as a way of saving the state of an object into a stream or buffer. For example, ASP.NET uses the XmlSerializer class to encode XML Web service messages.

The data in your objects is described using programming language constructs like classes, fields, properties, primitive types, arrays, and even embedded XML in the form of XmlElement or XmlAttribute objects. You have the option of creating your own classes, annotated with attributes, or using the the conceptual topic at MSDN: xmlschemadefinitiontoolxsdexe to generate the classes based on an existing XML Schema definition (XSD) document. If you have an XML Schema, you can run the Xsd.exe to produce a set of classes that are strongly typed to the schema and annotated with attributes to adhere to the schema when serialized.

To transfer data between objects and XML requires a mapping from the programming language constructs to XML Schema and vice versa. The XmlSerializer, and related tools like Xsd.exe, provide the bridge between these two technologies at both design time and run time. At design time, use the Xsd.exe to produce an XML Schema document (.xsd) from your custom classes, or to produce classes from a given schema. In either case, the classes are annotated with custom attributes to instruct the XmlSerializer how to map between the XML Schema system to the common language runtime. At run time, instances of the classes can be serialized into XML documents that follow the given schema. Likewise, these XML documents can be deserialized into run time objects. (Note that the XML Schema is optional, and not needed at design time or run time.)

To control the generated XML, you can apply special attributes to classes and members. For example, to specify a different XML element name, apply an XmlElementAttribute to a public field or property, and set the XmlElementAttribute.ElementName property. For a list of all attributes, see the conceptual topic at MSDN: attributesthatcontrolserialization.

If the XML generated must conform to section 5 of the World Wide Consortium (www.w3.org) document, "Simple Object Access Protocol (SOAP) 1.1", you must construct the XmlSerializer with an XmlTypeMapping. To further control the encoded SOAP XML, use the attributes listed in the conceptual topic at MSDN: attributesthatcontrolsoapencodedserialization.

With the XmlSerializer you can take advantage of working with strongly typed classes and still have the flexibility of XML. Using fields or properties of type XmlElement, XmlAttribute or XmlNode in your strongly typed classes, you can read parts of the XML document directly into XML objects.

If you work with extensible XML schemas, you can also use the XmlAnyElementAttribute and XmlAnyAttributeAttribute attributes to serialize and deserialize elements or attributes that are not found in the original schema. To use the objects, apply an XmlAnyElementAttribute to a field that returns an array of XmlElement objects, or apply an XmlAnyAttributeAttribute to a field that returns an array of XmlAttribute objects.

If a property or field returns a complex object (such as an array or a class instance), the XmlSerializer converts it to an element nested within the main XML document. For example, the first class in the following C# code returns an instance of the second class.

          public class MyClass
          {
           public MyObject MyObjectProperty;
          }
          public class MyObject
          {
           public string ObjectName;
          }

The serialized, XML output looks like this:

          <MyClass>
           <MyObjectProperty>
           <Objectname>My String</ObjectName>
           </MyObjectProperty>
          </MyClass>

You can also override the serialization of any set of objects and their fields and properties by creating one of the appropriate attributes, and adding it to an XmlAttributes. Overriding serialization in this way has two uses: first, you can control and augment the serialization of objects found in a DLL, even if you don't have access to the source; second, you can create one set of serializable classes, but serialize the objects in multiple ways. For more details, see the XmlAttributeOverrides class.

To serialize an object, call the XmlSerializer.Serialize method. To deserialize an object, call the XmlSerializer.Deserialize method.

To add XML namespaces to an XML document, see XmlSerializerNamespaces.

Note The XmlSerializer gives special treatment to classes that implement IEnumerable or ICollection. A class that implements IEnumerable must implement a public Add method that takes a single parameter. The Add method's parameter must be of the same type as is returned from the Current property on the value returned from GetEnumerator, or one of that type's bases. A class that implements ICollection (such as CollectionBase) in addition to IEnumerable must have a public Item indexed property (indexer in C#) that takes an integer, and it must have a public Count property of type integer. The parameter to the Add method must be the same type as is returned from the Item property, or one of that type's bases. For classes implementing ICollection, values to be serialized will be retrieved from the indexed Item property, not by calling GetEnumerator.

Example

The following example contains two main classes:


            PurchaseOrder

and


            Test

. The


            PurchaseOrder

class contains information about a single purchase. The


            Test

class contains the methods that create the purchase order, and that read the created purchase order.

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

/* The XmlRootAttribute allows you to set an alternate name 
   (PurchaseOrder) of the XML element, the element namespace; by 
   default, the XmlSerializer uses the class name. The attribute 
   also allows you to set the XML namespace for the element.  Lastly,
   the attribute sets the IsNullable property, which specifies whether 
   the xsi:null attribute appears if the class instance is set to 
   a null reference. */
[XmlRootAttribute("PurchaseOrder", Namespace="http://www.cpandl.com", 
IsNullable = false)]
public class PurchaseOrder
{
   public Address ShipTo;
   public string OrderDate; 
   /* The XmlArrayAttribute changes the XML element name
    from the default of "OrderedItems" to "Items". */
   [XmlArrayAttribute("Items")]
   public OrderedItem[] OrderedItems;
   public decimal SubTotal;
   public decimal ShipCost;
   public decimal TotalCost;   
}
 
public class Address
{
   /* The XmlAttribute instructs the XmlSerializer to serialize the Name
      field as an XML attribute instead of an XML element (the default
      behavior). */
   [XmlAttribute]
   public string Name;
   public string Line1;

   /* Setting the IsNullable property to false instructs the 
      XmlSerializer that the XML attribute will not appear if 
      the City field is set to a null reference. */
   [XmlElementAttribute(IsNullable = false)]
   public string City;
   public string State;
   public string Zip;
}
 
public class OrderedItem
{
   public string ItemName;
   public string Description;
   public decimal UnitPrice;
   public int Quantity;
   public decimal LineTotal;

   /* Calculate is a custom method that calculates the price per item,
      and stores the value in a field. */
   public void Calculate()
   {
      LineTotal = UnitPrice * Quantity;
   }
}
 
public class Test
{
   public static void Main()
   {
      // Read and write purchase orders.
      Test t = new Test();
      t.CreatePO("po.xml");
      t.ReadPO("po.xml");
   }

   private void CreatePO(string filename)
   {
      // Create an instance of the XmlSerializer class;
      // specify the type of object to serialize.
      XmlSerializer serializer = 
      new XmlSerializer(typeof(PurchaseOrder));
      TextWriter writer = new StreamWriter(filename);
      PurchaseOrder po=new PurchaseOrder();
       
      // Create an address to ship and bill to.
      Address billAddress = new Address();
      billAddress.Name = "Teresa Atkinson";
      billAddress.Line1 = "1 Main St.";
      billAddress.City = "AnyTown";
      billAddress.State = "WA";
      billAddress.Zip = "00000";
      // Set ShipTo and BillTo to the same addressee.
      po.ShipTo = billAddress;
      po.OrderDate = System.DateTime.Now.ToLongDateString();
 
      // Create an OrderedItem object.
      OrderedItem i1 = new OrderedItem();
      i1.ItemName = "Widget S";
      i1.Description = "Small widget";
      i1.UnitPrice = (decimal) 5.23;
      i1.Quantity = 3;
      i1.Calculate();
 
      // Insert the item into the array.
      OrderedItem [] items = {i1};
      po.OrderedItems = items;
      // Calculate the total cost.
      decimal subTotal = new decimal();
      foreach(OrderedItem oi in items)
      {
         subTotal += oi.LineTotal;
      }
      po.SubTotal = subTotal;
      po.ShipCost = (decimal) 12.51; 
      po.TotalCost = po.SubTotal + po.ShipCost; 
      // Serialize the purchase order, and close the TextWriter.
      serializer.Serialize(writer, po);
      writer.Close();
   }
 
   protected void ReadPO(string filename)
   {
      // Create an instance of the XmlSerializer class;
      // specify the type of object to be deserialized.
      XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
      /* If the XML document has been altered with unknown 
      nodes or attributes, handle them with the 
      UnknownNode and UnknownAttribute events.*/
      serializer.UnknownNode+= new 
      XmlNodeEventHandler(serializer_UnknownNode);
      serializer.UnknownAttribute+= new 
      XmlAttributeEventHandler(serializer_UnknownAttribute);
   
      // A FileStream is needed to read the XML document.
      FileStream fs = new FileStream(filename, FileMode.Open);
      // Declare an object variable of the type to be deserialized.
      PurchaseOrder po;
      /* Use the Deserialize method to restore the object's state with
      data from the XML document. */
      po = (PurchaseOrder) serializer.Deserialize(fs);
      // Read the order date.
      Console.WriteLine ("OrderDate: " + po.OrderDate);
  
      // Read the shipping address.
      Address shipTo = po.ShipTo;
      ReadAddress(shipTo, "Ship To:");
      // Read the list of ordered items.
      OrderedItem [] items = po.OrderedItems;
      Console.WriteLine("Items to be shipped:");
      foreach(OrderedItem oi in items)
      {
         Console.WriteLine("\t"+
         oi.ItemName + "\t" + 
         oi.Description + "\t" +
         oi.UnitPrice + "\t" +
         oi.Quantity + "\t" +
         oi.LineTotal);
      }
      // Read the subtotal, shipping cost, and total cost.
      Console.WriteLine("\t\t\t\t\t Subtotal\t" + po.SubTotal);
      Console.WriteLine("\t\t\t\t\t Shipping\t" + po.ShipCost); 
      Console.WriteLine("\t\t\t\t\t Total\t\t" + po.TotalCost);
   }
 
   protected void ReadAddress(Address a, string label)
   {
      // Read the fields of the Address object.
      Console.WriteLine(label);
      Console.WriteLine("\t"+ a.Name );
      Console.WriteLine("\t" + a.Line1);
      Console.WriteLine("\t" + a.City);
      Console.WriteLine("\t" + a.State);
      Console.WriteLine("\t" + a.Zip );
      Console.WriteLine();
   }

   protected void serializer_UnknownNode
   (object sender, XmlNodeEventArgs e)
   {
      Console.WriteLine("Unknown Node:" +   e.Name + "\t" + e.Text);
   }

   protected void serializer_UnknownAttribute
   (object sender, XmlAttributeEventArgs e)
   {
      System.Xml.XmlAttribute attr = e.Attr;
      Console.WriteLine("Unknown attribute " + 
      attr.Name + "='" + attr.Value + "'");
   }
}

System.Xml.Serialization.XmlSerializer Member List:

Public Constructors

ctor #2	Overloaded: `.ctor(Type type)` Initializes a new instance of the XmlSerializer class that can serialize objects of the specified type into XML documents, and vice versa.
ctor #3	Overloaded: `.ctor(XmlTypeMapping xmlTypeMapping)` Initializes an instance of the XmlSerializer class using an object that maps one type to another.
ctor #4	Overloaded: `.ctor(Type type, string defaultNamespace)` Initializes a new instance of the XmlSerializer class that can serialize objects of the specified type into XML documents, and vice versa. Specifies the default namespace for all the XML elements.
ctor #5	Overloaded: `.ctor(Type type, Type[] extraTypes)` Initializes a new instance of the XmlSerializer class that can serialize objects of the specified type into XML documents, and vice versa. If a property or field returns an array, the extraTypes parameter specifies objects that can be inserted into the array.
ctor #6	Overloaded: `.ctor(Type type, XmlAttributeOverrides overrides)` Initializes a new instance of the XmlSerializer class that can serialize objects of the specified type into XML documents, and vice versa. Each object to be serialized can itself contain instances of classes, which this overload can override with other classes.
ctor #7	Overloaded: `.ctor(Type type, XmlRootAttribute root)` Initializes a new instance of the XmlSerializer class that can serialize objects of the specified type into XML documents, and vice versa. Specifies the class to use as the XML root element.
ctor #8	Overloaded: `.ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, string defaultNamespace)` Initializes a new instance of the XmlSerializer class that can serialize objects of type Object into XML document instances, and vice versa. Each object to be serialized can itself contain instances of classes, which this overload can override with other classes. This overload also specifies the default namespace for all the XML elements, and the class to use as the XML root element.

Public Methods

CanDeserialize	Gets a value indicating whether this XmlSerializer can deserialize a specified XML document.
Deserialize	Overloaded: `Deserialize(Stream stream)` Deserializes the XML document contained by the specified Stream.
Deserialize	Overloaded: `Deserialize(TextReader textReader)` Deserializes the XML document contained by the specified TextReader.
Deserialize	Overloaded: `Deserialize(XmlReader xmlReader)` Deserializes the XML document contained by the specified XmlReader.
Equals (inherited from System.Object)	See base class member description: System.Object.Equals Derived from System.Object, the primary base class for all objects.
FromMappings
FromTypes	Returns an array of XmlSerializer objects created from an array of types.
GetHashCode (inherited from System.Object)	See base class member description: System.Object.GetHashCode Derived from System.Object, the primary base class for all objects.
GetType (inherited from System.Object)	See base class member description: System.Object.GetType Derived from System.Object, the primary base class for all objects.
Serialize	Overloaded: `Serialize(Stream stream, object o)` Serializes the specified Object and writes the XML document to a file using the specified Stream.
Serialize	Overloaded: `Serialize(TextWriter textWriter, object o)` Serializes the specified Object and writes the XML document to a file using the specified TextWriter.
Serialize	Overloaded: `Serialize(XmlWriter xmlWriter, object o)` Serializes the specified Object and writes the XML document to a file using the specified XmlWriter.
Serialize	Overloaded: `Serialize(Stream stream, object o, XmlSerializerNamespaces namespaces)` Serializes the specified Object and writes the XML document to a file using the specified Stream, referencing the specified namespaces.
Serialize	Overloaded: `Serialize(TextWriter textWriter, object o, XmlSerializerNamespaces namespaces)` Serializes the specified Object and writes the XML document to a file using the specified TextWriter, referencing the specified namespaces.
Serialize	Overloaded: `Serialize(XmlWriter xmlWriter, object o, XmlSerializerNamespaces namespaces)` Serializes the specified Object and writes the XML document to a file using the specified XmlWriter, referencing the specified namespaces.
ToString (inherited from System.Object)	See base class member description: System.Object.ToString Derived from System.Object, the primary base class for all objects.

Public Events

UnknownAttribute	Occurs when the XmlSerializer encounters an XML attribute of unknown type during deserialization.
UnknownElement	Occurs when the XmlSerializer encounters an XML element of unknown type during deserialization.
UnknownNode	Occurs when the XmlSerializer encounters an XML node of unknown type during deserialization.
UnreferencedObject	Occurs during deserialization of a SOAP-encoded XML stream, when the XmlSerializer encounters a recognized type that is not used (unreferenced).

Protected Constructors

ctor #1 Overloaded:
.ctor()Default constructor. This constructor is called by derived class constructors to initialize state in this type.
Constructs a new instance of the XmlSerializer class.

Protected Methods

CreateReader	Returns an object used to read the XML document to be serialized.
CreateWriter	Supports the Shared Source CLI infrastructure and is not intended to be used directly from your code
Deserialize	Overloaded: `Deserialize(XmlSerializationReader reader)` Supports the Shared Source CLI infrastructure and is not intended to be used directly from your code
Finalize (inherited from System.Object)	See base class member description: System.Object.Finalize Derived from System.Object, the primary base class for all objects.
MemberwiseClone (inherited from System.Object)	See base class member description: System.Object.MemberwiseClone Derived from System.Object, the primary base class for all objects.
Serialize	Overloaded: `Serialize(object o, XmlSerializationWriter writer)` Supports the Shared Source CLI infrastructure and is not intended to be used directly from your code

Hierarchy:

System.Object

System.Xml.Serialization.XmlSerializer

System.Xml.Serialization.XmlSerializer Member Details

Overloaded ctor #1

Summary: Constructs a new instance of the XmlSerializer class.

This type supports the Shared Source CLI infrastructure and is not intended to be used directly from your code.

Default constructor. This constructor is called by derived class constructors to initialize state in this type.

C# Syntax:


            protected XmlSerializer();