How to Use XmlSerializer to serialize in C#

Steps to Serialize Objects in C# Using XmlSerializer

1. Define the class to serialize: First, create the class that you want to serialize. The class must have public properties or fields that you want to include in the XML. Optionally, you can use attributes like [XmlElement] and [XmlIgnore] to control how the XML is generated.

2. Create an instance of XmlSerializer: You will create an instance of the XmlSerializer class, passing the type of the object to be serialized.

3. Serialize the object: Use the Serialize method of the XmlSerializer instance to convert the object into XML.

4. Write the XML to a file or string: You can either serialize the object to a string using a StringWriter, or you can write it directly to a file using a StreamWriter.

How to serialize an object using XmlSerializer in C#?

For example, Using XmlSerializer to Serialize a Book Object.

static string GetXml(object obj)
{
	XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType());

	using (var writer = new StringWriter())
	{
		xmlSerializer.Serialize(writer, obj);
		return writer.ToString();
	}
}

You’ll need to ensure the class you want to serialize has the [Serializable] attribute:

[Serializable]
public class Book
{
	public string Title { get; set; }
	public string Author { get; set; }
	public int YearPublished { get; set; }
	public List<string> Genres { get; set; }
}

Creating a Book Object and Serializing It

static void Main(string[] args)
{
	var book = new Book()
	{
		Title = "The Lean Startup",
		Author = "Eric Ries",
		YearPublished = 2011,
		Genres = new List<string> { "Business", "Entrepreneurship", "Technology" }
	};

	string xml = GetXml(book);
	Console.WriteLine(xml);
}

Output XML:

<?xml version="1.0" encoding="utf-16"?>
<Book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Title>The Lean Startup</Title>
  <Author>Eric Ries</Author>
  <YearPublished>2011</YearPublished>
  <Genres>
    <string>Business</string>
    <string>Entrepreneurship</string>
    <string>Technology</string>
  </Genres>
</Book>

Customizing the Serialization:

If you'd like to modify the output in different ways, here are some possible changes:

1. Removing the Namespace Attribute: By default, the XML includes the xmlns:xsi namespace.

To remove it, you can pass an XmlSerializerNamespaces object with XmlQualifiedName.Empty:

static string GetXml(object obj)
{
 XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType());

 using (var writer = new StringWriter())
 {
 	xmlSerializer.Serialize(writer, obj, new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty }));
 	return writer.ToString();
 }
}

Output:

<?xml version="1.0" encoding="utf-16"?>
<Book>
  <Title>The Lean Startup</Title>
  <Author>Eric Ries</Author>
  <YearPublished>2011</YearPublished>
  <Genres>
    <string>Business</string>
    <string>Entrepreneurship</string>
    <string>Technology</string>
  </Genres>
</Book>

2. Change the Encoding to UTF-8: To change the encoding from UTF-16 to UTF-8, you can subclass StringWriter:

public class Utf8StringWriter : StringWriter
{
    public override Encoding Encoding => Encoding.UTF8;
}

Then use this in your serialization method:

static string GetXml(object obj)
{
 XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType());

 using (var writer = new Utf8StringWriter())
 {
 	xmlSerializer.Serialize(writer, obj, new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty }));
 	return writer.ToString();
 }
}

Output:

<?xml version="1.0" encoding="utf-8"?>
<Book>
  <Title>The Lean Startup</Title>
  <Author>Eric Ries</Author>
  <YearPublished>2011</YearPublished>
  <Genres>
    <string>Business</string>
    <string>Entrepreneurship</string>
    <string>Technology</string>
  </Genres>
</Book>

3. Exclude a Property from Serialization: If you don't want to serialize the Genres property, you can use the [XmlIgnore] attribute:

[Serializable]
public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    public int YearPublished { get; set; }
    
    [XmlIgnore]
    public List<string> Genres { get; set; }
}

Output:

<?xml version="1.0" encoding="utf-8"?>
<Book>
  <Title>The Lean Startup</Title>
  <Author>Eric Ries</Author>
  <YearPublished>2011</YearPublished>
</Book>

4. Change Property Name in XML: You can change the serialized property name using the [XmlElement] attribute.

For example, you can change YearPublished to PublishedYear:

[Serializable]
public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    [XmlElement("PublishedYear")]
    public int YearPublished { get; set; }
    public List<string> Genres { get; set; }
}

Output:

<?xml version="1.0" encoding="utf-8"?>
<Book>
  <Title>The Lean Startup</Title>
  <Author>Eric Ries</Author>
  <PublishedYear>2011</PublishedYear>
  <Genres>
    <string>Business</string>
    <string>Entrepreneurship</string>
    <string>Technology</string>
  </Genres>
</Book>

Note: When using XmlWriter, you don't need to apply the [Serializable] attribute to your class. This allows you to serialize any class, including third-party classes that don't have this attribute. However, keep in mind that XmlWriter doesn't consider attributes like [XmlIgnore], so all properties will be serialized unless manually excluded.

In this example, I showed how you can use XmlSerializer with a Book class, and how you can customize serialization by modifying encoding, changing property names, excluding properties, and removing namespace attributes from the XML output.