Failing to read XML content using XmlSerializer

Question

I got this in my class:

namespace MSAToolsLibrary.PublisherEntry
{
    [XmlRoot(ElementName = "PublisherDatabase", Namespace = "http://www.publictalksoftware.co.uk/msa")]
    public class PublisherData
    {
        public PublisherData()
        {
            //_Publishers = new List<Publisher>();
            _PublishersDictionary = new Dictionary<string, Publisher>();
        }

        public List<Publisher> Publishers
        {
            get { return _PublishersDictionary.Select(x => x.Value).ToList(); }
            set { _PublishersDictionary = value.ToDictionary(x => x.Name, x => x); }
        }
        private Dictionary<string, Publisher> _PublishersDictionary;

        [XmlIgnore]
        public Dictionary<string, Publisher> PublisherDictionary
        {
            get { return _PublishersDictionary; }
        }


        public void AddPublisher(String strName, String strNotes, Gender eGender, Appointed eAppointedAs, Serving eServingAs, bool bUseForDemonstrations, bool bAvailableMidweek, bool bAvailableWeekend, DateTime[] listDatesNotAvailable)
        {
            Publisher _Publisher = new Publisher()
            {
                Name = strName,
                Notes = strNotes,
                Gender = eGender,
                AppointedAs = eAppointedAs,
                ServingAs = eServingAs,
            };

            _Publisher.Assignments.UseForDemonstrations = bUseForDemonstrations;
            _Publisher.Availability.Midweek = bAvailableMidweek;
            _Publisher.Availability.Weekend = bAvailableWeekend;
            _Publisher.Availability.DatesNotAvailable = new List<DateTime>(listDatesNotAvailable);

            //_Publishers.Add(_Publisher);
            _PublishersDictionary.Add(strName, _Publisher);
        }
    }
}

Now, when I save my data to XML it all works good.

But when I read in:

public void ReadPublisherData(out Int64 iResult)
{
    _PublisherData.Publishers.Clear(); // Reset

    iResult = MakeResult(true);

    try
    {
        XmlSerializer x = new XmlSerializer(_PublisherData.GetType());
        using (StreamReader reader = new StreamReader(_strPathXML))
        {
            _PublisherData = (PublisherData)x.Deserialize(reader);
            iResult = _PublisherData.PublisherDictionary.Count;
        }
    }
    catch
    {
        iResult = MakeResult(false);
    }
 }

Doesn't work. I have zero publishers in the list or the dictionary.

What am I doing wrong?

Update

If I change the PublisherData declaration so that it has the needed back field:

public PublisherData()
{
    _Publishers = new List<Publisher>();
    _PublishersDictionary = new Dictionary<string, Publisher>();
}

public List<Publisher> Publishers
{
    get => _Publishers; set => _Publishers = value;
}
private List<Publisher> _Publishers;

Then this causes the data to serialize correctly and I get what is expected in the MFC application. But now my PublisherDictionary is hanging. So I added a function:

   public void BuildPublisherDictionary()
    {
        _PublishersDictionary = _Publishers.ToDictionary(x => x.Name, x => x);
    }

And adjusted the read routine:

   public void ReadPublisherData(out Int64 iResult)
    {
        iResult = MakeResult(true);

        try
        {
            _PublisherData.Publishers.Clear(); // Reset

            XmlSerializer x = new XmlSerializer(_PublisherData.GetType());
            using (StreamReader reader = new StreamReader(_strPathXML))
            {
                _PublisherData = (PublisherData)x.Deserialize(reader);

                _PublisherData.BuildPublisherDictionary();
                iResult = _PublisherData.PublisherDictionary.Count;
            }
        }
        catch
        {
            iResult = MakeResult(false);
        }
     }

It works. But I don't know if that is the simplest way. My problem with the above is that the list / dictionary are now detached from each other. So if I add a publisher to the dictionary it will now not be in the list.

Update 2

At the moment, after reading in the XML, if I add or remove a Publisher I am applying it to both the list and the dictionary. Unless there is a simpler way.

Answer 1

The serializer will only call the getter of your List and then call Add for each element it finds, providing it the instance of the type it deserialized from that element.

If your requirement is to have both a list and a dictionary you'll have to provide an implementation of an type that does so and implements an applicable interface.

The following ListDict uses a List and a Dictionary as their backing stores while implementing IList to be used in the (de)serializtion.

public class ListDict<K, T>:IList<T>
{

   public Dictionary<K, T> dict = new Dictionary<K, T>();
   public List<T> list = new List<T>();
   Func<T,K> KeyFunc;

   // takes an Function that returns a key for T
   public ListDict(Func<T,K> keyfunc) 
   {
      KeyFunc = keyfunc;
   } 

   // called by the serializer
   public void Add(T value) 
   {
      Add( KeyFunc(value), value);
   }

   // fill both List and Dictionary
   public void Add(K key, T value) 
   {
      list.Add(value);
      dict.Add( key , value);
   }
   // left out other required methods from IList<T>
}

Now your PublisherData class will change as follows to leverage above class:

[XmlRoot(ElementName = "PublisherDatabase", Namespace = "http://www.publictalksoftware.co.uk/msa")]
public class PublisherData
{
    private ListDict<string, Publisher> _PublishersDictionary;
    public PublisherData()
    {
        // provide the function to generate a key for a Publisher
        _PublishersDictionary = new ListDict<string,Publisher>( (p) => p.Name  );   
    }

    [XmlElement]
    public ListDict<string,Publisher> Publishers
    { 
        get { return _PublishersDictionary; }
    }


    [XmlIgnore]
    public Dictionary<string, Publisher> PublisherDictionary
    {
        get {return _PublishersDictionary.dict; }
    }
}

Using above classes gives me a filled list and Dictionary directly after deserialization. You'll have to make sure of course to keep the backing stores in sync in the ListDict. Maybe you can do without it but that depends on your exact usecase.