C# Parameterless Constructor on inherited class

Question

Hopefully a simple question

I need to serialise an inherted class, in this example iProperty inherits from 'PropertyDescriptor'. In order to achieve this iProperty needs a parameter less constructor, and the base class has no such constructor, If I attempt to add a construtor I am told the base class does not contain a method thats takes 0 arguments which is correct. How do I get round this issue.

Thanks.

Example

   public class iProperty : PropertyDescriptor
    {
        private string propName;
        private object propValue;

        // Need Parameterless Construtor ?

        public iProperty(string pName, object pValue)
            : base(pName, new Attribute[] { })
        {
            propName = pName;
            propValue = pValue;

        }
    }

I think we need to see the PropertyDescriptor class (or at least its constructor). — Jashaszun
– Jashaszun, Commented Jul 31, 2015 at 15:33
You may have to make a serializable wrapper for iProperty, with a method GetiProperty or equivalent that creates the iProperty object based on the serialized info. There's no working around the constructor requirement. — zneak
– zneak, Commented Jul 31, 2015 at 15:35
Please show your iProperty parameterless constructor. This could call one of the existing PropertyDescriptor constructors with default values. — Polyfun
– Polyfun, Commented Jul 31, 2015 at 15:37
So if I was to make iProperty an external class so it could be serialised how would I integrate that class into the above code? Thanks — Sarah T
– Sarah T, Commented Jul 31, 2015 at 15:53
You can use Composition instead of Inheritance and mark PropertyDescriptor field with attribute '[XmlIgnore]'. Or change PropertyDescriptor to be an interface. Or create a parameterless constructor for PropertyDescriptor. It is really depends on your architecture and restrictions. — LaoR
– LaoR, Commented Aug 4, 2015 at 15:17

Igor · Accepted Answer · 2015-07-31 15:36:39Z

7

public class iProperty : PropertyDescriptor
{
    private string propName;
    private object propValue;

    // Need Parameterless Construtor ?
    public iProperty()
        : base("placeholder", new Attribute[] { })
    {
    }

    public iProperty(string pName, object pValue)
        : base(pName, new Attribute[] { })
    {
        propName = pName;
        propValue = pValue;

    }
}

answered Jul 31, 2015 at 15:36

Igor

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1 Comment

Sarah T Over a year ago

Thanks, already tried this , it reports 'There was an error reflecting type'

Ondra · Accepted Answer · 2015-07-31 15:37:49Z

3

You can create a parameterless contructor, but you have to call one of base class contructors anyway

public class iProperty : PropertyDescriptor
{

    public iProperty()
        : base(someDefaults)
    {
    }
}

You can also implement a parameterless constructor in the base class and make it protected. That way no-one except the derived class can call it.

answered Jul 31, 2015 at 15:37

Ondra

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3 Comments

Sarah T Over a year ago

Does not work as it causes exception on serialisation - 'Error reflecting type'

Sarah T Over a year ago

How can I add a constructor to the base class which is part of dotnet?

Ondra Over a year ago

I tought that PropertyDescription is your class. If it is dotnets, then you cant add a constructor.

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