How to deserialize an XML array containing multiple types of elements in C#

Question

I'm trying to deserialize the following file:

<league>
    <players>
        <skater>
            <name>Wayne Stamkos</name>
            <goals>23</goals>
            <assists>34</assists>
        </skater>
        <skater>
            <name>Sidney Lindros</name>
            <goals>41</goals>
            <assists>44</assists>
        </skater>
        <goalie>
            <name>Martin Roy</name>
            <wins>15</wins>
            <losses>12</losses>
        </goalie>
        <skater>
            <name>Paul Forsberg</name>
            <goals>21</goals>
            <assists>51</assists>
        </skater>
        <goalie>
            <name>Roberto Rinne</name>
            <wins>18</wins>
            <losses>23</losses>
        </goalie>
    </players>
</league>

With the following code:

namespace ConsoleApplication2
{
    [XmlRoot("league")]
    public class League
    {
        [XmlArray("players")]
        [XmlArrayItem("skater")]
        public List<Skater> skaters { get; set; }
        [XmlArrayItem("goalie")]
        public List<Goalie> goalies { get; set; }
    }

    public class Skater
    {
        [XmlElement("name")]
        public string Name;
        [XmlElement("goals")]
        public int Goals;
        [XmlElement("assists")]
        public int Assists;
    }

    public class Goalie
    {
        [XmlElement("name")]
        public string Name;
        [XmlElement("wins")]
        public int Wins;
        [XmlElement("losses")]
        public int Losses;
    }

    class Program
    {
        static void Main(string[] args)
        {
            using (FileStream reader = new FileStream(@"C:\Temp\test.xml", FileMode.Open, FileAccess.Read))
            {
                var ser = new XmlSerializer(typeof(League));
                League league = (League)ser.Deserialize(reader);
            }
        }
    }
}

I'm expecting to get back a League object containing a Skaters list with 3 elements and a Goalies list with 2 elements. I do get the expected Skaters list but the Goalies list is empty. What am I doing wrong?

you need an interface common to Goalie and Skater, then you can have a single array of these. — Alex
– Alex, Commented Nov 21, 2013 at 22:12
@Marc Gravell: The file can contain 0 to N goalies and skaters. — ChrisB
– ChrisB, Commented Nov 21, 2013 at 22:28
@ChrisB d'oh; if I used my eyes I could have answered that myself ;p — Marc Gravell
– Marc Gravell, Commented Nov 21, 2013 at 22:32

Marc Gravell · Accepted Answer · 2013-11-21 22:29:10Z

39

There are two ways to do this; the first is to do something like:

[XmlArray("players")]
[XmlArrayItem("skater", Type=typeof(Skater))]
[XmlArrayItem("goalie", Type=typeof(Goalie))]
public List<SomeCommonBaseClass> Players { get; set; }

which maps the two element types inside a single collection. Worst case, SomeCommonBaseClass could be object:

[XmlArray("players")]
[XmlArrayItem("skater", Type=typeof(Skater))]
[XmlArrayItem("goalie", Type=typeof(Goalie))]
public List<object> Players { get; set; }

The second is to make <players> map to a wrapper object:

[XmlElement("players")]
public Players Players { get;set;}
...
public class Players
{
    [XmlElement("skater")]
    public List<Skater> Skaters {get;set;}

    [XmlElement("goalie")]
    public List<Goalie> Goalies {get;set;}
}

Which to choose depends on the circumstance; the latter allows things like "at most one goalie", by changing it to:

    [XmlElement("goalie")]
    public Goalie Goalie {get;set;}

answered Nov 21, 2013 at 22:29

Marc Gravell

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2 Comments

ChrisB Over a year ago

Since I really need 2 separate lists, solution 2 seems to be my only alternative. Thanks!

T-moty Over a year ago

The second solution is a very elegant way to accomplish that. +1

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