XML cannot be serialized - parameterless constructor error, even with constructor

Question

I'm trying to serialize an object to xml using XmlSerializer but keep getting this error:

System.InvalidOperationException: [MySql.Data.MySqlClient.MySqlParameter] cannot be serialized because it does not have a parameterless constructor.

I followed the solution to why xml serializable class need a parameterless constructor which seems to have solved the problem for everyone else, but I still get an error. When I add public MyClass() it gives me 'MyClass.MyClass()' must declare a body because it is not marked abstract, extern, or partial, so I add a body and the first error comes back.

Note that originally there aren't any constructors, parameterless or otherwise, so I don't understand why it isn't just automatically creating its own.

What am I doing wrong?

Code added:

MyFile.cs

public async Task Save(MyClass xmlObj)
{
    XmlSerializer xmlSer = new XmlSerializer(this.GetType()); //I think the problem is likely to be here
    StringWriter strWriter = new StringWriter();

    xmlSer.Serialize(strWriter, xmlObj);
    objToUpdate.ColName = (strWriter.ToString());
    await dbContext.SaveChangesAsync();
}

File.cs

public async Task<IActionResult> SaveData(params...)
{
    await new MyFile<MySqlParameter>(accessParam, dbContext).Save(xmlObj);
}

The issue is surely that MySqlParameter can't be serialised, not MyClass - so why are you adding a constructor to MyClass? And what version of MySql are you using? Because MySqlParameter does have a parameterless constructor. Can you post a compilable reproduction of your problem? — Matthew Watson
– Matthew Watson, Commented Feb 20, 2020 at 8:45
Why would it be trying to serialise MySqlParameter? That's only the data being sent to the db when saving, it's in the parent method, not with the XmlSerializer — half of a glazier
– half of a glazier, Commented Feb 20, 2020 at 9:13
are you tried to change your constructor to private or internal? — Mohammed Sajid
– Mohammed Sajid, Commented Feb 20, 2020 at 9:26
Why would it be trying to serialise - I don't know why, but the error message clearly states that it is being serialised. You will need to post some code. — Matthew Watson
– Matthew Watson, Commented Feb 20, 2020 at 9:29

David Hinchliffe · Accepted Answer · 2020-02-20 09:08:19Z

1

You should have added

public MyClass(){}

to the class. There is a difference between no body and an empty body which is what you want on this constructor.

answered Feb 20, 2020 at 9:08

David Hinchliffe

5002 silver badges6 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

half of a glazier Over a year ago

From my question: so I add a body and the first error comes back - I already tried that

David Hinchliffe Over a year ago

as @Matthew asked, please post the code for the class you're trying to serialize, it does look like you trying to serialize a none searilizable object

half of a glazier · Accepted Answer · 2020-02-20 09:45:10Z

1

I figured it out...

I had been creating a new XmlSerializer and passing in a parameter as posted in a SO answer:

XmlSerializer xmlSer = new XmlSerializer(this.GetType());

When really it works perfectly fine to use the same XmlSerializer as the deserialization:

XmlSerializer objSer = new XmlSerializer(typeof(MyClass));

answered Feb 20, 2020 at 9:45

half of a glazier

2,1122 gold badges27 silver badges53 bronze badges

Collectives™ on Stack Overflow

XML cannot be serialized - parameterless constructor error, even with constructor

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related