how to copy a baseclass to an endclass without reference?

Question

I am trying to write a method that can copy an existing class into a new one, but without a reference to the source class.
There are many samples out there, but in my case the source and target objects are defined as a baseclass while they are created as an endclass.

My classes are like this

// my baseclass
public partial class ModelBase
{
    [JsonIgnore]
    public RowStatus Status { get; set; }
}

// one of my endclasses
public class ModelUser: BaseClasses.ModelBase
{
    public int? UserID { get; set; }

    public string UserFirst { get; set; }

    public string UserLastname { get; set; }
}

// and there are many more that derive from ModelBase off course...

What I would like is that in a Base Form (where all other forms will derive from) I can copy an existing model into a new one, without a reference to the existing one.
So I tried to do this using serializing/deserializing, which works well, but only if you know the exact type, and in my BaseForm I do not have the exact type yet, there I work with an instance declared as ModelBase, but created in a derived form as ModelUser for example.

In other words, I have a base form like this

public partial class FormMVBaseDetail
{
    protected ModelBase model = null;
    protected ModelBase _originalModel = null;
    ...

    private void FormMVBaseDetail_Shown(object sender, EventArgs e)
    {
        _originalModel = CloneModel(model);
    }

    protected ModelBase CloneModel(ModelBase model)
    {
        string json = JsonConvert.SerializeObject(model);
        return JsonConvert.DeserializeObject<ModelBase>(json);
    }
}

public partial class FormMVBaseUser : FormMVBaseDetail
{
    model = new ModelUser();
    ...
    // somewhere in the code some properties of model could change...

    private void button1_Click(object sender, EventArgs e)
    {
        // Now I would like that _originalModel is an exact copy of model
        // So _originalModel should be of type ModelUser, not ModelBase
        // How to achieve that without additional code in FormMBaseUser ?
     
        if (_originalModel.UserFirst != model.UserFirst)
        { // do something }
    }
}

The first attempt is this

public ModelBase CloneModel(ModelBase model)
{
    string json = JsonConvert.SerializeObject(model);
    return JsonConvert.DeserializeObject<ModelBase>(json);
}

this has the problem that, allthough the parameter model is created as new ModelUser() the deserialize will make it a ModelBase which only has one public property, the Status.

If I would do this, then it would work, but only for ModelUser

public ModelBase CloneModel(ModelBase model)
{
    string json = JsonConvert.SerializeObject(model);
    return JsonConvert.DeserializeObject<ModelUser>(json);
}

This is not usefull in a baseform.
So the next thing I tried is this

public object CloneModel(ModelBase model)
{
    string json = JsonConvert.SerializeObject(model);
    return JsonConvert.DeserializeObject<object>(json);
}

The idea was to use it like this

ModelBase _originalModel = null;
_originalModel = (ModelBase)CloneModel(CurrentModel);

but for some reason it always deserializes as Newtonsoft.Json.Linq.JObject in stead of object, so this also does not works for me.

How could I achieve this ?

I have read this links, but they did not get me any further

How do I use reflection to call a generic method?
Passing just a type as a parameter in C#
How can I use an expression tree to call a generic method when the Type is only known at runtime?
Use variable as Type

Do you know the concrete type in runtime? For same from install will it be always same concrete type? — Ygalbel, Sep 09 '21 at 14:26
@Ygalbel no, it can be any class that derives from ModelBase — GuidoG, Sep 09 '21 at 14:27
You could make the base class generic: public partial class FormMVBaseDetail where T : ModelBase { public T CloneModel(T model) { var json = JsonConvert.SerializeObject(model); return JsonConvert.DeserializeObject(json); } } — Andrew McClement, Sep 09 '21 at 14:28
Might be tedious (and I might miss something obvious) but why not simply write copy constructors in your endclasses that take the baseclass as argument and perform deep copy of the properties? — Roland Deschain, Sep 09 '21 at 14:28
@AndrewMcClement That is also in the links I wrote at the bottom of my question, but I can't get it to compile/work. Maybe an example of how to do this in this case ? — GuidoG, Sep 09 '21 at 14:29
@RolandDeschain Do you have an example of how to do that ? If I have 100 classes derived from ModelBase I don't want to write 100 methods to do this off course — GuidoG, Sep 09 '21 at 14:30
Yeah, just realized my idea doesn't make much sense in this scenario, sorry. — Roland Deschain, Sep 09 '21 at 14:37

score 1 · Accepted Answer · answered Sep 09 '21 at 14:29

1

You can use the non-generic version of JsonConvert.DeserializeObject()

It take the string in first parameter and the type in second one.

So your clone function will be like this:

public object CloneModel(ModelBase model)
{
    string json = JsonConvert.SerializeObject(model);
    return JsonConvert.DeserializeObject(json, model.GetType());
}

answered Sep 09 '21 at 14:29

Ygalbel

5,214
1
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Compile fine for me – Ygalbel Sep 09 '21 at 14:31
1

Sorry I had a typo, works for me also now, thanks you – GuidoG Sep 09 '21 at 14:33

Andrew McClement · Answer 2 · 2021-09-09T14:43:06.470

1

The generic version of Ygalbel's answer would be this:

public partial class FormMVBaseDetail<T> where T : ModelBase
{
    protected T _model;
    protected T _originalModel;

    public T CloneModel(T model)
    {
       var json = JsonConvert.SerializeObject(model);
       return JsonConvert.DeserializeObject<T>(json);
    }
}

Whether you want the base class to be generic will depend on your needs.

Usage:

public partial class FormMVBaseUser : FormMVBaseDetail<ModelUser>
{
    _model = new ModelUser();
    // Other code as before

edited Sep 09 '21 at 14:43

answered Sep 09 '21 at 14:37

Andrew McClement

1,171
5
14

How do I call this method for my situation ? – GuidoG Sep 09 '21 at 14:38
Sorry, I'll add an example derived class – Andrew McClement Sep 09 '21 at 14:41
Though this might work (have not tested yet) I like the answer of Ygalbel more. It seems more simple to me. Maybe someone can explain the differences between these 2 approaches and which would be the better one ? I'll up this answer anyway off course – GuidoG Sep 09 '21 at 14:51
@GuidoG The most obvious difference to highlight is that using generics (``) allows the derived types to be used everywhere. No casting from `object` to `ModelBase` is needed when cloning; no casting from `ModelBase` to `ModelUser` is needed within the derived class `FormMVBaseUser`. – Sean Skelly Sep 09 '21 at 17:27

how to copy a baseclass to an endclass without reference?

2 Answers2