C# Serialize a class with a List data member

Wednesday, March 30, 2011 by Nate Bross

Someone asked on Stack Overflow:

I have this c# class:

public class Test
{
    public Test() { }

    public IList<int> list = new List<int>();
}

Then I have this code:

        Test t = new Test();
        t.list.Add(1);
        t.list.Add(2);

        IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication();
        StringWriter sw = new StringWriter();
        XmlSerializer xml = new XmlSerializer(t.GetType());
        xml.Serialize(sw, t);

When I look at the output from sw, its this:

<?xml version="1.0" encoding="utf-16"?>
<Test xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" />

the values 1,2 I added to the list member variable dont show up.

1. So how can I fix this ? I made the list a property but it still doesnt seem to work.
2. I am using xml serialization here, are there any other serializers ?
3. I want performance! Is this the best approach ?

--------------- UPDATE BELOW -------------------------

So the actual class I want to serialize is this:

public class RoutingResult
    {
        public float lengthInMeters { get; set; }
        public float durationInSeconds { get; set; }

        public string Name { get; set; }

        public double travelTime
        {
            get
            {
                TimeSpan timeSpan = TimeSpan.FromSeconds(durationInSeconds);
                return timeSpan.TotalMinutes;
            }
        }

        public float totalWalkingDistance
        {
            get
            {
                float totalWalkingLengthInMeters = 0;
                foreach (RoutingLeg leg in Legs)
                {
                    if (leg.type == RoutingLeg.TransportType.Walk)
                    {
                        totalWalkingLengthInMeters += leg.lengthInMeters;
                    }
                }

                return (float)(totalWalkingLengthInMeters / 1000);
            }
        }

        public IList<RoutingLeg> Legs { get; set; } // this is a property! isnit it?
        public IList<int> test{get;set;} // test ...

        public RoutingResult()
        {
            Legs = new List<RoutingLeg>();
            test = new List<int>(); //test
            test.Add(1);
            test.Add(2);
            Name = new Random().Next().ToString(); // for test
        }
    }

But the XML produced by the serializer is this:

<RoutingResult>
  <lengthInMeters>9800.118</lengthInMeters>
  <durationInSeconds>1440</durationInSeconds>
  <Name>630104750</Name>
</RoutingResult>

???

its ignoring both of those lists ?

I posted the following answer, which was chosen as the accepted answer and received 4 upvotes:

1) Your list is a field, not a property, and the XmlSerializer will only work with properties, try this:

public class Test
{    
    public Test() { IntList = new List<int>() }    
    public IList<int> IntList { get; set; }
}

2) There are other Serialiation options, Binary the main other one, though there is one for JSON as well.

3) Binary is probably the most performant way, since it is typically a straight memory dump, and the output file will be the smallest.

Originally posted on Stack Overflow — 4 upvotes (accepted answer). Licensed under CC BY-SA.