Conditional xml serialization

Alternative :

• Switch your public fields to properties
• Define default values with the DefaultValueAttribute attribute
• Define content property with the ContentPropertyAttribute attribute
• Use XamlWriter/XamlReader

You end up with something like this:

 [ContentProperty("Books")]
 public class Library {

   private readonly List<Book> m_books = new List<Book>();

   public List<Book> Books { get { return m_books; } }

 }

 public class Book
 {

    [DefaultValue(string.Empty)]
    public string Title { get; set; }

    [DefaultValue(string.Empty)]
    public string Description { get; set; }

    [DefaultValue(string.Empty)]
    public string Author { get; set; }

 }

You should be able to use the ShouldSerialize* pattern:

public class Book
{
    [XmlAttribute] 
    public string Title {get;set;}

    public bool ShouldSerializeTitle() {
        return !string.IsNullOrEmpty(Title);
    }

    [XmlAttribute]
    public string Description {get;set;}

    public bool ShouldSerializeDescription() {
        return !string.IsNullOrEmpty(Description );
    }

    [XmlAttribute]
    public string Author {get;set;}

    public bool ShouldSerializeAuthor() {
        return !string.IsNullOrEmpty(Author);
    }

    [XmlAttribute]
    public string Publisher {get;set;}

    public bool ShouldSerializePublisher() {
        return !string.IsNullOrEmpty(Publisher);
    }
}

public class Books
{
    [XmlElement("Book")]
    public List<Book> BookList;
}

public class Book
{
    [XmlAttribute]
    public string Title;
    [XmlAttribute]
    public string Description;
    [XmlAttribute]
    public string Author;
    [XmlAttribute]
    public string Publisher;
}

class Program
{
    static void Main()
    {
        var books = new Books
        {
            BookList = new List<Book>(new[] 
            {
                new Book 
                {
                    Title = "t1",
                    Description = "d1"
                },
                new Book 
                {
                    Author = "a2",
                    Description = "d2"
                },
                new Book 
                {
                    Author = "a3",
                    Title = "t3",
                    Publisher = "p3"
                },
            })
        };

        var serializer = new XmlSerializer(books.GetType());
        serializer.Serialize(Console.Out, books);
    }
}

And if you want to remove the namespace from the root node:

var namespaces = new XmlSerializerNamespaces();
namespaces.Add(string.Empty, string.Empty);
serializer.Serialize(Console.Out, books, namespaces);

Also I would recommend you using properties instead of fields in your model classes for better encapsulation:

public class Books
{
    [XmlElement("Book")]
    public List<Book> BookList { get; set; }
}