[XmlType(TypeName = "") not being serialize

Question

I have this class that has a property that is a array of another class type

 [XmlRoot(ElementName = "student")]
public class Student
{
    [XmlElement(ElementName = "name")]
    public string Name { get; set; }

    [XmlElement(ElementName = "email")]
    public string Email { get; set; }

    [XmlIgnoreAttribute]
    public string Department { get; set; }

    [XmlElement(ElementName = "topics")]
    public Topic[] Topics { get; set; }
}

[XmlType(TypeName = "topic")]
public class Topic
{
    [XmlElement(ElementName = "topiccode")]
    public string TopicName;
}

When I try to serialize this into an XML it is messing the top tag that is the parent of Topic code. So while I expect to get this

<student>
  <name>Max Power</name>
  <email>test999@email.com</email>
  <topics>
    <topic>
        <topiccode>CAGLENN_17</topiccode>
    </topic>
  </topics>
</student> 

What I get instead is the topic tag is omitted

<student>
  <name>Max Power</name>
  <email>test999@email.com</email>
  <topics>
    <topiccode>CAGLENN_17</topiccode>
  </topics>
</student> 

Is there a different option I am suppose to use, or maybe I am not setting something correctly?

Answer 1

Solution

You need to change to use [XmlArray(ElementName = "topics")]:

[XmlArray(ElementName = "topics")]
public Topic[] Topics { get; set; }

Try it online

Explanation

The reason is that by using [XmlElement(ElementName = "topics")] you are telling the serializer that you don't want a containing element, and that each entry should exist in the main object.

We can see this in action if we add a second topic:

<?xml version="1.0" encoding="utf-16"?>
<student xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <name>Max power</name>
  <email>test999@email.com</email>
  <topics>
    <topiccode>CAGLENN_17</topiccode>
  </topics>
  <topics>
    <topiccode>CAGLENN_18</topiccode>
  </topics>
</student>

[XmlArray(ElementName = "topics")], on the other hand, specifies the name for the element that contains the array's items.