将对象序列化为 XML 数组

Question

I have a scenario where I may need to serialize an object as a root element into an XML file or if a file is provided that already has an array of objects I need to serialize the object into the array.

Because the object may be a root I have decorated it with the System.Xml.Serialization.XmlRootAttribute .

When I serialize the object to an XElement I get the root version of the object. When I add the XElement to the array it retains the namespace attributes and can not be deserialized properly.

Here is a portion of the class:

[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.8.3928.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="urn:www.agxml.org:schemas:all:4:0", TypeName = "CommodityMovement")]
[System.Xml.Serialization.XmlRootAttribute(ElementName ="CommodityMovement", Namespace="urn:www.agxml.org:schemas:all:4:0", IsNullable=false)]
public partial class CommodityMovementType {
    ...
}

When I create a file with a list it works just fine.

    private static String CreateMessageFile<T>(String filePath, T message)
    {
        var xmlDoc = new XDocument();
        // serialize XML to string to the xmlEntity document
        using (var writer = new StringWriter())
        {
            var entitySerializer = new XmlSerializer(typeof(List<T>));
            var list = new List<T>();
            list.Add(message);
            entitySerializer.Serialize(writer, list);
            xmlDoc.Add(XElement.Parse(writer.ToString()));
        }
        xmlDoc.Save(filePath);
    }

This will serialize an array with one message:

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfCommodityMovement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <CommodityMovement>
        ...
    </CommodityMovement>
</ArrayOfCommodityMovement>

However, I may read that file and add a message to that array.

    private static String CreateMessageFile<T>(String filePath, T message)
    {
        var xmlDoc = new XDocument();
        using var sourceStream = File.Open(filePath,FileMode.Open);
        xmlDoc.Add(XElement.Load(sourceStream));
        using (var writer = new StringWriter())
        {
            var entitySerializer = new XmlSerializer(entity.DotNetType);
            // entitySerializer.Serialize(writer, list);
            entitySerializer.Serialize(writer, message);
            xmlDoc.Root.Add(XElement.Parse(writer.ToString()));
        }
        xmlDoc.Save(filePath);
    }

This produces the the following XML:

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfCommodityMovement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <CommodityMovement>
        ...
    </CommodityMovement>
    <CommodityMovement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="urn:www.agxml.org:schemas:all:4:0">
        ...
    </CommodityMovement>
</ArrayOfCommodityMovement>

When I attempt to deserialize the ArrayOfCommodityMovement it only deserializes the first CommodityMovement message.

If I open the generated XML file and remove the namespace attributes from the second CommodityMovement element then it will deserialize correctly. Here is the test I am using to define "correctly".

            XDocument xDocument = XDocument.Load(filePath);
            var descendants = xDocument.Descendants("CommodityMovement");
            Assert.Equal(2, descendants.Count());

            var entitySerializer = new XmlSerializer(typeof(List<CommodityMovementType>));
            var commodityMovementList = entitySerializer.Deserialize(xDocument.CreateReader()) as List<CommodityMovementType>;
            Assert.NotEmpty(commodityMovementList);
            Assert.Equal(2, commodityMovementList.Count);

So how can I deserialize the object and insert the resulting element into an existing array and make sure the attributes aren't added?

BTW, I need to keep the System.Xml.Serialization.XmlRootAttribute because depending on configuration I need to be able to generate one message per file and the CommodityMovement then becomes a root element.

Note: This isn't my exact code. It is a simplified example.

Thanks in advance for any help.

Answer 1

I found the solution is to remove the attributes and namespace if this is not the first element in the array. To see if it is the first I check to see if the document root is null:

if (xmlDoc.Root is null)

If it is not null, I serialize the element, remove it's attributes and namespace and add the element to the root element:

else
{
    var element = SerializeEntityAsElement(entity, masterData);
    // remove attributes and namespace so element can be added to existing array
    element.RemoveAttributes();
    element.Name = element.Name.LocalName;

    xmlDoc.Root.Add(element);
}

Now my test will pass:

XDocument xDocument = XDocument.Load(filePath);
var descendants = xDocument.Descendants("CommodityMovement");
Assert.Equal(2, descendants.Count());

var entitySerializer = new XmlSerializer(typeof(List<CommodityMovementType>));
var commodityMovementList = entitySerializer.Deserialize(xDocument.CreateReader()) as List<CommodityMovementType>;
Assert.NotEmpty(commodityMovementList);
Assert.Equal(2, commodityMovementList.Count);