C#•10mo ago

✅ DataContractSerializer with polymorphisme

Hello everyone. I need help with a topic. I would like to serialize this XML file:

<?xml version="1.0" encoding="utf-8" ?>
<DataBase>
  <Movie Title="Matrix">
    <Duration>110</Duration>
  </Movie>
  <Movie Title="IronMan">
  </Movie>
  <Movie Title="Test">
  </Movie>
</DataBase>

<?xml version="1.0" encoding="utf-8" ?>
<DataBase>
  <Movie Title="Matrix">
    <Duration>110</Duration>
  </Movie>
  <Movie Title="IronMan">
  </Movie>
  <Movie Title="Test">
  </Movie>
</DataBase>

Here's my class that contains my database

[DataContract(Name = "DataBase", Namespace = "")]
public class VideoDataBase
{
    [DataMember] // ????
    public List<Movie> Movies { get; set; }
    
    [OnDeserializing]
    public void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("Database on Deserializing");
    }
    
    [OnDeserialized]
    public void OnDeserialized(StreamingContext context)
    {
        Console.WriteLine("Database has been deserialized");
    }
    

}

[DataContract(Name = "DataBase", Namespace = "")]
public class VideoDataBase
{
    [DataMember] // ????
    public List<Movie> Movies { get; set; }
    
    [OnDeserializing]
    public void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("Database on Deserializing");
    }
    
    [OnDeserialized]
    public void OnDeserialized(StreamingContext context)
    {
        Console.WriteLine("Database has been deserialized");
    }
    

}

and my generic class

[DataContract]
[KnownType(typeof(Movie))]
public abstract class VideoDatabaseItem
{
    [DataMember]
    public string Title { get; set; }
    
    [OnDeserializing]
    public void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("VideoDatabaseItem on Deserializing");
    }

}

[DataContract]
[KnownType(typeof(Movie))]
public abstract class VideoDatabaseItem
{
    [DataMember]
    public string Title { get; set; }
    
    [OnDeserializing]
    public void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("VideoDatabaseItem on Deserializing");
    }

}

and finally my Movie Class, which is a derived class of VideoDatabaseItem.

[DataContract]
public class Movie : VideoDatabaseItem
{
    [DataMember(Name = "Duration")]
    public string Duration { get; set; }
    
    [DataMember(Name = "Title")]
    public string Title { get; set; }
    
    [OnDeserializing]
    public new void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("Movie on Deserializing");
    }
}

[DataContract]
public class Movie : VideoDatabaseItem
{
    [DataMember(Name = "Duration")]
    public string Duration { get; set; }
    
    [DataMember(Name = "Title")]
    public string Title { get; set; }
    
    [OnDeserializing]
    public new void OnDeserializing(StreamingContext context)
    {
        Console.WriteLine("Movie on Deserializing");
    }
}

I'm having trouble serializing my list with the Movie item, for example. I feel like the inheritance isn't working properly. I absolutely want to have a generic class for my list of items because later on, I want to be able to serialize other objects. It would be great if one of you could help me with this topic 🙏🏻

12 Replies

Pobiega•10mo ago

I'm not familiar with [DataContract] deserialization, must it use that or is the [XmlElement] family of attributes an acceptable replacement?

Unknown User•10mo ago

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jessica BoisserandOP•10mo ago

Can I use XmlElement in a WPF project with polymorphic objects? I got the impression that DataContracts were more appropriate, am I mistaken ?

Pobiega•10mo ago

If you are just reading/writing from/to an .XML file on disk, you absolutely can DataContracts seem to be related to WCF, as far as I can tell

jessica BoisserandOP•10mo ago

ahah is just a basic test 🙂

Pobiega•10mo ago

Well, if you actually want a file-based database for your WPF app, might I suggest SQLite? 🙂

Unknown User•10mo ago

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Pobiega•10mo ago

We will help you with polymorphic XML deserialization, if that is the root of your problem here, but if your root problem is actually that you want a file based database, there are much better approaches

jessica BoisserandOP•10mo ago

Sorry, I made a mistake with WPF, but I meant to refer to WCF here... Unfortunately, the topic is imposed, and I cannot choose SQLite, i know it's quite sad 😢 mhmhmmh okey I've been stuck for a while despite many attempts; I must not be approaching it in the right way 😬

Pobiega•10mo ago

Okay if its WCF you dont have much of an option I think but for the record, here is how I'd do it with "normal" xml

public class Movie : DbEntry
{
    [XmlAttribute]
    public string Title { get; set; }
    [XmlElement]
    public int? Duration { get; set; }
}

public class Database
{
    [XmlElement(nameof(Movie), typeof(Movie))]
    [XmlElement(nameof(Comic), typeof(Comic))]
    public List<DbEntry> Elements { get; set; }
}

public class Comic : DbEntry
{
    [XmlAttribute]
    public string Text { get; set; }
}

public abstract class DbEntry
{
}

public class Movie : DbEntry
{
    [XmlAttribute]
    public string Title { get; set; }
    [XmlElement]
    public int? Duration { get; set; }
}

public class Database
{
    [XmlElement(nameof(Movie), typeof(Movie))]
    [XmlElement(nameof(Comic), typeof(Comic))]
    public List<DbEntry> Elements { get; set; }
}

public class Comic : DbEntry
{
    [XmlAttribute]
    public string Text { get; set; }
}

public abstract class DbEntry
{
}

that works fine for this xml:

<?xml version="1.0" encoding="utf-8" ?>
<Database>
    <Movie Title="Matrix">
        <Duration>110</Duration>
    </Movie>
    <Movie Title="IronMan">
    </Movie>
    <Comic Text="Yes">
        BodyContent
    </Comic>
</Database>

<?xml version="1.0" encoding="utf-8" ?>
<Database>
    <Movie Title="Matrix">
        <Duration>110</Duration>
    </Movie>
    <Movie Title="IronMan">
    </Movie>
    <Comic Text="Yes">
        BodyContent
    </Comic>
</Database>

As far as I can tell, DataContractSerializer doesn't support polymorphism without using a type discriminator or hm, maybe... Well, its not possible with that XML structure DataContracts dont allow "inline arrays", so you must have an explicit list wrapper Its a fucking mess thou for sure 😄

jessica BoisserandOP•10mo ago

Thank you very much for your help !!! 🙏🏻 I was really stuck! I'm currently testing your solution, but it seems to be what I want to do. 🙃 perfect, it's work for me !! Thannnk youu 🙂

Unknown User•10mo ago

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✅ DataContractSerializer with polymorphisme