How to remove an <ArrayOfX> container element when serializing a List<T> into an existing XML document

Question

I have these classes:

public class WikiEntry
{
    public string Id { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }
    [XmlArray]
    public List<Category> Categories { get; set; }
}

public class Category
{
    [XmlAttribute]
    public string Id { get; set; }
    [XmlAttribute]
    public string Text { get; set; }
}

At the beginning I have this XML structure:

<Wiki>
  <Categories></Categories>
  <Tags></Tags>
  <WikiEntries></WikiEntries>
</Wiki>

And I am serializing wiki.Categories and adding it into the existing XML like this:

var xDoc = XDocument.Load("Data.xml");

WikiEntry wiki = new WikiEntry
{
   Id = Guid.NewGuid().ToString(),
   Title = "Simple title",
   Content = "Simple content here",
   Categories = new List<Category>
     {
       new Category
       {
         Id = Guid.NewGuid().ToString(),
         Text = "CATEGORYA"
       },
       new Category
       {
         Id = Guid.NewGuid().ToString(),
         Text = "CATEGORYB"
       }
    }
};

var categories = xDoc.Root.Element("Categories");

var categoriesBuilder = new StringBuilder();

using (var writer = XmlWriter.Create(categoriesBuilder, new XmlWriterSettings { Indent = true, ConformanceLevel = ConformanceLevel.Auto, OmitXmlDeclaration = true }))
        {
            var ns = new XmlSerializerNamespaces();
            ns.Add("", "");

            var xs = new XmlSerializer(typeof(List<Category>), "");

            xs.Serialize(writer, wiki.Categories, ns);
        }

categories.Add(XElement.Parse(categoriesBuilder.ToString().Trim()));
xDoc.Save(file);

The problem is that when I do I get this:

<Categories>
 <ArrayOfCategory>
   <Category Id="482ce9f6-5d4c-48f9-b84f-33c3cf9b0b0f" Text="CATEGORYA" />
   <Category Id="73e6c671-fb6d-40a4-8694-1d5dbcf381d5" Text="CATEGORYB" />
 </ArrayOfCategory>
 <ArrayOfCategory>
   <Category Id="3c0f2a15-4623-4f33-b356-75e8c8b89624" Text="CATEGORYA" />
   <Category Id="d8720ca9-06f5-401d-90e2-c7f43e1c91f5" Text="CATEGORYB" />
 </ArrayOfCategory>

So, my question is how can I serialize my Category class , so that I get this (omitting the <ArrayOfCategory> parent):

  <Categories>
      <Category Id="482ce9f6-5d4c-48f9-b84f-33c3cf9b0b0f" Text="CATEGORYA" />
      <Category Id="73e6c671-fb6d-40a4-8694-1d5dbcf381d5" Text="CATEGORYB" />
      <Category Id="3c0f2a15-4623-4f33-b356-75e8c8b89624" Text="CATEGORYA" />
      <Category Id="d8720ca9-06f5-401d-90e2-c7f43e1c91f5" Text="CATEGORYB" />
  </Categories>

Note: I want to remove it, not rename it.

Can you post your complete code include how categoriesBuilder and wikis are being instantiated? — Mehdi Ibrahim
– Mehdi Ibrahim, Commented Aug 31, 2018 at 4:37
Are you looking for Deserializing into a List without a container element in XML? — dbc
– dbc, Commented Sep 1, 2018 at 18:30

dbc · Accepted Answer · 2018-09-01 19:41:21Z

You can serialize directly into an XDocument by using XContainer.CreateWriter(). This in turn will allow you to serialize directly into a child XElement of your categories element without any intermediate string representation.

First, define the following extension method:

public static class XObjectExtensions
{
    public static XElement SerializeToXElement<T>(this T obj, XContainer parent = null, XmlSerializer serializer = null, XmlSerializerNamespaces ns = null)
    {
        if (obj == null)
            throw new ArgumentNullException();
        // Initially, write to a fresh XDocument to cleanly avoid the exception described in
        // https://stackoverflow.com/questions/19045921/net-xmlserialize-throws-writestartdocument-cannot-be-called-on-writers-created
        var doc = new XDocument();
        using (var writer = doc.CreateWriter())
        {
            (serializer ?? new XmlSerializer(obj.GetType())).Serialize(writer, obj, ns ?? NoStandardXmlNamespaces());
        }
        // Now move to the incoming parent.
        var element = doc.Root;
        if (element != null)
        {
            element.Remove();
            if (parent != null)
            {
                parent.Add(element);
            }
        }
        return element;
    }

    public static XmlSerializerNamespaces NoStandardXmlNamespaces()
    {
        var ns = new XmlSerializerNamespaces();
        ns.Add("", ""); // Disable the xmlns:xsi and xmlns:xsd lines.
        return ns;
    }
}

Now you can add the Categories of your WikiEntry to your xDoc as follows:

var categories = xDoc.Root.Element("Categories");
foreach (var category in wiki.Categories)
{
    category.SerializeToXElement(categories);
}

Working sample .Net fiddle here.

Roman Svitukha · Accepted Answer · 2018-08-31 04:51:26Z

0

Passing the root name as argument to the XMLSerializer call can do the trick.

XmlSerializer serializer = new XmlSerializer(typeof(List), new XmlRootAttribute("RootElementName"));

answered Aug 31, 2018 at 4:51

Roman Svitukha

1,4021 gold badge14 silver badges23 bronze badges

1 Comment

Kaloyan Drenski Over a year ago

Clever, but no, it just makes inner element the same name as the outer, parent node, like so <Categories><Categories><Category></Category</Categories></Categories>

Mehdi Ibrahim · Accepted Answer · 2018-08-31 15:51:13Z

0

Here is some Linq-to-Xml to achieve what you are looking for:

categories.Add(XElement.Parse(categoriesBuilder.ToString().Trim()));


XDocument output =
new XDocument(
    new XElement(xDoc.Root.Name,
        new XElement("Categories",
            from comp in xDoc.Root.Elements("Categories").Elements("ArrayOfCategory").Elements("Category")
            select new XElement("Category",
                new XAttribute("Id", comp.Attribute("Id").Value),
                new XAttribute("Text", comp.Attribute("Text").Value)
            ))));




output.Save("c:\\so\\test.xml");

answered Aug 31, 2018 at 15:51

Mehdi Ibrahim

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4 Comments

Mehdi Ibrahim Over a year ago

Does the solution address your needs?

Kaloyan Drenski Over a year ago

I've already used LINQ-to-XML, but wasn't what I was looking for. Still, thanks for the suggestion!

Mehdi Ibrahim Over a year ago

No problem, although it's impossible to think why this would not work for you. Next time be specific in your question if you are avoiding a solution so people here aren't wasting time trying to help you with something you dont need.

Kaloyan Drenski Over a year ago

I am not "avoiding" a solution. I was specific enough for @dbc to actually help me solve my problem.

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