.net – XmlSerializer and Collection property with private setter

netxml-serialization

Say I have a simple class like so

[Serializeable]
public class MyClass
{
    public MyClass()
    {
       this.MyCollection = new List<int>();
    }


    public List<int> MyCollection { get; private set;}
}

If I try to deserialize this using XmlSerializer I get an error saying that MyCollection is readonly and cannot be assigned to. However I don't want to make the setter public as this can cause all kinds of problems if the user of the class assigns to it. FxCop rightly warns against this: Collection properties should be read only

However on the bottom of the page in the community added content is this:

XmlSerializer understands read-only
collections Collection
properties do not have to be
read-write for the XmlSerializer to
serialize and deserialize the contents
correctly. The XmlSerializer will look
for a method called Add on collection
properties that implement ICollection
or IEnumerable, and use that to
populate the collection when
deserializing an instance of the owner
type.

However it just doesn't seem to be the case (as I get the InvalidOperationException). What am I able to do that obeys the best practice of keeping the property setter private while still allowing me to use the XmlSerializer?

Best Answer

Your private setter is causing the issue. The XmlSerializer class will work fine with the class I have given below. The XmlSerializer class was invented before private setters were introduced, so it is probably not checking that correctly when it scans the class type using reflection. Maybe you should report this to Microsoft as a bug.

public class MyClass
{
    private List<int> _myCollection;

    public MyClass()
    {
        _myCollection = new List<int>();
    }

    public List<int> MyCollection
    {
        get
        {
            return this._myCollection;
        }
    }
}
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