Cannot serialize XML from an API response. System.InvalidOperationException: 'There is an error in XML document (1, 2).'

Question

I am currently doing a project related to a formula 1 API but sadly I cannot figure out how to serialize my xml content into an object.

The XML I am trying to serialize : https://pastebin.com/nkt9EA1k

My API request and the attempt to serialize it.

        client = new HttpClient();
        HttpResponseMessage response = client.GetAsync("http://ergast.com/api/f1/2022").Result;
        HttpContent responseContent = response.Content;
        XmlSerializer serializer = new XmlSerializer(typeof(Wrapper));
        Wrapper wrapper2;
        string result = File.ReadAllText("temp.txt");//hc.ReadAsStringAsync().Result;
        using (TextReader reader = new StringReader(result))
        {
            wrapper2 = (Wrapper)serializer.Deserialize(reader);
        }
        if(wrapper2 != null)
        {
            SecondWrapper wrapper = wrapper2.MRData;
            string outPut = wrapper.Season;
            foreach (Race r in wrapper.RaceTable)
            {
                outPut += $"\n{r.RaceName}\t{r.Date}\t{r.Circuit.CircuitName}";
            }
            File.WriteAllText("Output.txt", outPut);
        }

My Wrapper class :

public class Wrapper
{
    public SecondWrapper MRData;
}

My SecondWrapper Class :

public class SecondWrapper
{
    public string Season;
    public Race[] RaceTable;
}

My Race class :

public class Race
{
    public string RaceName { set; get; }
    public Circuit Circuit { set; get; }
    public string Date;
    public string Time;
    public StepDateTime FirstPractice { set; get; }
    public StepDateTime SecondPractice { set; get; }
    public StepDateTime ThirdPractice { set; get; }
    public StepDateTime Qualifying { set; get; }
    public StepDateTime Sprint { set; get; }
}

My Circuit class :

public class Circuit
{
    public string CircuitName { set; get; }
    public Location Location { set; get; }
}

My Location class :

public class Location
{
    public double lat { set; get; }
    [XmlAttribute("long")]
    public double Long { set; get; }
    public string Locality { set; get; }
    public string Country { set; get; }
}

My StepDateTime class :

public class StepDateTime
{
    public string Date { set; get; }
    public string Time { set; get; }
}

I tried to make a text file where I deleted the first 2 lines of the XML answer hoping it would fix the issue but it didn't.

PS : I know I'm not using propreties and I am not respecting the c# conventions for the classes but it is temporary just so I can find a way to fix the issue. It is also my first time working with xml answers so I might have done some obvious errors.

Thanks for the help.

.NET has an XSD tool that allows you to generate a schema and then C# classes for the schema instead of having to rely on writing the C# yourself. — Martin Honnen, May 30 '22 at 09:00
Your classes don't correspond do your XML. You can auto-generate your classes from the XML as shown in [Generate C# class from XML](https://stackoverflow.com/q/4203540). For instance if I upload your XML to https://xmltocsharp.azurewebsites.net/ I get a plausible set of classes. You will need to deserialize to `[XmlRoot(ElementName="MRData", Namespace="http://ergast.com/mrd/1.5")] public class MRData { /* Properties omitted */ }` — dbc, May 30 '22 at 13:23
Yes, to **agree** with @dbc, adding an `XmlRoot` attribute as shown in that comment at least gets past the `System.InvalidOperationException`. See: [Deserializing Twitter XML](https://stackoverflow.com/a/1557145/5438626) and [There is an error in XML document](https://stackoverflow.com/a/12672746/5438626) — IVSoftware, May 30 '22 at 15:01

IVSoftware · Answer 1 · 2022-05-31T13:33:10.557

You have XML from an API response and your question is How to serialize my xml content into an object. Here's an approach using Newtonsoft.Json NuGet to parse the XML-to-JSON with the JsonConvert.SerializeXNode method then JSON-to-Wrapper.

(Compared to answers using the XmlSerializer this seems a tad more forgiving on the Xml parse.)

string plaintext;
using (StreamReader sr = new StreamReader(
    new WebClient().OpenRead("http://ergast.com/api/f1/2022")))
{
    plaintext = sr.ReadToEnd();
}
        
// vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
// Two steps instead of one because IJW.
// XElement parse takes any valid XML (i.e. does not enforce a schema).
XElement xel = XElement.Parse(plaintext);
// Convert the XNode to Json text.
var jsontext =  JsonConvert.SerializeXNode(
        xel, 
        Formatting.Indented); // More readable.
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

// JsonConvert is very fault tolerant. It deserializes the
// properies in the model, ignores those that aren't, and
// won't break if queried for properties that it can't provide.
var wrapper = (Wrapper)JsonConvert.DeserializeObject<Wrapper>(jsontext);

Added/changed these classes and used Race, Circuit Location and StepDateTime as-is:

public class Wrapper
{
    public MRData MRData { get; set; }
}

public class MRData
{
    public RaceTable RaceTable{ get; set; }
}
public class RaceTable
{
    [JsonProperty(propertyName:"@season")]
    public string Season { get; set; }

    [JsonProperty(propertyName: "Race")]
    public Race[] Races { get; set; }
}

Test Code

Console.WriteLine($"Races for the {wrapper.MRData.RaceTable.Season} season.");
Console.WriteLine($"Found {wrapper.MRData.RaceTable.Races.Length} races");
var race0 = wrapper.MRData.RaceTable.Races[0];
Console.WriteLine($"{race0.RaceName} is on {race0.Circuit.CircuitName}");

Output

Download this code from GitHub

Cannot serialize XML from an API response. System.InvalidOperationException: 'There is an error in XML document (1, 2).'

1 Answers1