Serialize Entity Framework object with children to XML file

Question

I'm querying data with parent/child result sets using Entity Framework and I want to export this data to an XML document.

var agreement = storeops.Agreements.SingleOrDefault(a => a.AgreementNumber == AgreementTextBox.Text);
XmlSerializer serializer = new XmlSerializer(agreement.GetType());
XmlWriter writer = XmlWriter.Create("Agreement.xml");
serializer.Serialize(writer, agreement);

This works well except it only serializes the parent without including the related child records in the XML. How can I get the children to serialize as well?

I also tried using POCO generated code and the child collections attempt to be serialized except they are ICollections which can't be serialized.

Cannot serialize member DataSnapshots.Agreement.AgreementItems of type System.Collections.Generic.ICollection`1[[DataSnapshots.AgreementItem, DataSnapshots, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] because it is an interface.

Solution

XML serialization behaves differently than binary serialization and data contract serialization when working with Entity Framework entities. The latter will serialize any related objects that have been loaded into the object graph, but XML serialization does not, so you will need to use a DataContractSerializer:

var agreement = storeops.Agreements.SingleOrDefault(a => a.AgreementNumber == AgreementTextBox.Text);
// make sure any relations are loaded

using (XmlWriter writer = XmlWriter.Create("Agreement.xml"))
{
    DataContractSerializer serializer = new DataContractSerializer(agreement.GetType());
    serializer.WriteObject(writer, agreement);
}

Also, Entity Framework uses lazy loading by default for 1:Many relations, and if the referenced objects haven't already been loaded when you go to serialize, then all you'll get is the keys that refer to them. You have to explicitly load the related entities either by calling agreement.Children.Load() or by using .Include("Children") in your query (where "Children" is the name of the collection of related entities).

Comments

[Brett Mathe]

I actually am getting children because my counts for them are greater than 0 but for some reason they aren't being serialized in the XmlSerializer. I'm guessing this is because the child object isn't truly a collection class but a EntityCollection which doesn't inherit from any Collection class.

[Joel C]

EntityCollection is defined as public sealed class EntityCollection<TEntity> : RelatedEnd, ICollection<TEntity>, IEnumerable<TEntity>, IEnumerable, IListSource, so it definitely is a collection.

[Brett Mathe]

Ok I see that so why isn't the child collection being serialized into the XML document? All of the other properties are there and loaded except for the children. The reason why I say EntityCollection doesn't behave like other collecions is because I can't reference the children using []. I think because of this the children aren't being serialized.

[Joel C]

I updated my answer. An XmlSerializer won't work the way you want, but you can easily use a DataContractSerializer because EF generates the DataContract for you.