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XmlSerializer Constructor (Type, XmlAttributeOverrides, Type[], XmlRootAttribute, String)

Initializes a new instance of the XmlSerializer class that can serialize objects of type Object into XML document instances, and deserialize XML document instances into objects of type Object. Each object to be serialized can itself contain instances of classes, which this overload overrides 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.

Namespace:  System.Xml.Serialization
Assembly:  System.Xml (in System.Xml.dll)

public XmlSerializer(
	Type type,
	XmlAttributeOverrides overrides,
	Type[] extraTypes,
	XmlRootAttribute root,
	string defaultNamespace


Type: System.Type
The type of the object that this XmlSerializer can serialize.
Type: System.Xml.Serialization.XmlAttributeOverrides
An XmlAttributeOverrides that extends or overrides the behavior of the class specified in the type parameter.
Type: System.Type[]
A Type array of additional object types to serialize.
Type: System.Xml.Serialization.XmlRootAttribute
An XmlRootAttribute that defines the XML root element properties.
Type: System.String
The default namespace of all XML elements in the XML document.

The overrides parameter allows for the creation of an XmlSerializer that serializes a class that extends or overrides the behavior of a base class. For example, given a DLL, it is possible to create a class that inherits or extends a class contained in the DLL. To serialize such a class, you must use an instance of the XmlAttributeOverrides class when constructing the XmlSerializer. For more details, see XmlAttributeOverrides.

By default, if a public property or field returns an object, or array of objects, the object types are automatically serialized. However, if a class contains a field or property that returns an array of type Object, any object can be inserted into that array. In that case, the XmlSerializer must be instructed to expect all the possible object types that are inserted into the Object array. To do this, use the extraTypes parameter to specify the extra object types to serialize or deserialize.

The root element of an XML document encloses all the other elements. By default, the object specified by the type parameter is serialized as the root element. Properties, such as the XML element name of the root element are taken from the type object. However, the root parameter allows you to replace the default object's information by specifying an XmlRootAttribute; the object allows you to set a different namespace, element name, and so on.

Use the defaultName parameter to specify the default namespace of all XML elements generated by the XmlSerializer.

The following example serializes an instance of a class that is defined in a DLL and to do so, overrides the public members found in the class. The example also specifies an array of extra types, the default namespace for all XML elements, and the class to use that provides the XML root element information. The example assumes that the code at the beginning has been compiled into a DLL named HighSchool.

// Beginning of the HighSchool.dll 

namespace HighSchool
   public class Student
      public string Name;
      public int ID;

   public class MyClass
      public Student[] Students;

namespace College
   using System;
   using System.IO;
   using System.Xml;
   using System.Xml.Serialization; 
   using HighSchool;

    public class Graduate:HighSchool.Student
       public Graduate(){}
       // Add a new field named University.
       public string University;
       // Use extra types to use this field.
       public object[]Info;

    public class Address
       public string City;

    public class Phone
       public string Number;

   public class Run
      public static void Main()
         Run test = new Run();

      private void WriteOverriddenAttributes(string filename)
         // Writing the file requires a TextWriter.
         TextWriter myStreamWriter = new StreamWriter(filename);
         // Create an XMLAttributeOverrides class.
         XmlAttributeOverrides attrOverrides = 
         new XmlAttributeOverrides();
         // Create the XmlAttributes class.
         XmlAttributes attrs = new XmlAttributes();
         /* Override the Student class. "Alumni" is the name
         of the overriding element in the XML output. */

         XmlElementAttribute attr = 
         new XmlElementAttribute("Alumni", typeof(Graduate));
         /* Add the XmlElementAttribute to the collection of
         elements in the XmlAttributes object. */
         /* Add the XmlAttributes to the XmlAttributeOverrides. 
         "Students" is the name being overridden. */
         "Students", attrs);

         // Create array of extra types.
         Type [] extraTypes = new Type[2];

         // Create an XmlRootAttribute.
         XmlRootAttribute root = new XmlRootAttribute("Graduates");

         /* Create the XmlSerializer with the 
         XmlAttributeOverrides object. */
         XmlSerializer mySerializer = new XmlSerializer
         (typeof(HighSchool.MyClass), attrOverrides, extraTypes,
         root, "");

         MyClass myClass= new MyClass();

         Graduate g1 = new Graduate();
         g1.Name = "Jacki";
         g1.ID = 1;
         g1.University = "Alma";

         Graduate g2 = new Graduate();
         g2.Name = "Megan";
         g2.ID = 2;
         g2.University = "CM";

         Student[] myArray = {g1,g2};

         myClass.Students = myArray;

         // Create extra information.
         Address a1 = new Address();
         a1.City = "Ionia";
         Address a2 = new Address();
         a2.City = "Stamford";
         Phone p1 = new Phone();
         p1.Number = "555-0101";
         Phone p2 = new Phone();
         p2.Number = "555-0100";

         Object[]o1 = new Object[2]{a1, p1};
         Object[]o2 = new Object[2]{a2,p2};

         g1.Info = o1;
         g2.Info = o2;

      private void ReadOverriddenAttributes(string filename)
         /* The majority of the code here is the same as that in the
         WriteOverriddenAttributes method. Because the XML being read
         doesn't conform to the schema defined by the DLL, the
         XMLAttributesOverrides must be used to create an 
         XmlSerializer instance to read the XML document.*/

         XmlAttributeOverrides attrOverrides = new 
         XmlAttributes attrs = new XmlAttributes();
         XmlElementAttribute attr = 
         new XmlElementAttribute("Alumni", typeof(Graduate));
         "Students", attrs);

         Type [] extraTypes = new Type[2];
         extraTypes[0] = typeof(Address);
         extraTypes[1] = typeof(Phone);

         XmlRootAttribute root = new XmlRootAttribute("Graduates");

         XmlSerializer readSerializer = new XmlSerializer
         (typeof(HighSchool.MyClass), attrOverrides, extraTypes,
         root, "");

         // A FileStream object is required to read the file. 
         FileStream fs = new FileStream(filename, FileMode.Open);

         MyClass myClass;
         myClass = (MyClass) readSerializer.Deserialize(fs);

         /* Here is the difference between reading and writing an 
         XML document: You must declare an object of the derived 
         type (Graduate) and cast the Student instance to it.*/
         Graduate g;
         Address a;
         Phone p;
         foreach(Graduate grad in myClass.Students)
            g = (Graduate) grad;
            Console.Write(g.Name + "\t");
            Console.Write(g.ID + "\t");
            Console.Write(g.University + "\n");
            a = (Address) g.Info[0];
            p = (Phone) g.Info[1];

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.