Option: Add an ignore attribute

[marcelltoth]

This issue is a followup on @IgorMamushin's feature request in #3.

The original request goes:

Ignore some properties. (Usually for ignore property used attributes. It will be well if we can set our ignore attribute, for example "JsonIgnore").
I did it in my fork. It is worked. But i did it wrong, it broke design.

[marcelltoth]

Thank you for providing feedback.

This is a very reasonable request, I'll be happy to accept a PR on it if you fix up your fork, or I can implement it myself when I'll have the time.

I definitely would not like adding Newtonsoft.Json as a dependency just for this attribute, (or any other library - dependencies have a high maintenance cost when authoring libraries.). So ignoring should happen using a custom attribute class. I'm not great at naming things, CloneIgnore maybe?

There is also another question. Not cloning a property can mean two very different things to me:

• Instead of deep cloning it, keep the original, so clone.SomeIgnoredProp == original.SomeIgnoredProp
• Set it to null / 0, so clone.SomeIgnoredProp == default

Which is the preferred semantics here? Or should it be configurable? (We can make it configurable in a simple way using the attribute)

[IgorMamushin]

If setting will have "Type" then you don't needed add Newtonsoft.Json. And i can use it like this:

ObjectCloner.Clone(myObject, new Settings 
{
    IgnorAttributeType = typeof(JsonIgnoreAttribute)
});

Actually if cloner will have itself attribute, it will be OK.

[marcelltoth]

Implementing settings is a tad more complicated than just using a custom attribute, but of course sooner or later it will need to be done.

What about my other question?

[IgorMamushin]

About second question.
I think it will good if we can select this in attribute.
I think it can be useful sometimes. But default value must will "clone.SomeIgnoredProp == default".

[enkodellc]

I need this, it is cloning my primary key which I do not want.

[IgorMamushin]

Hi, @enkodellc! You may watch my fork: https://github.com/IgorMamushin/ObjectCloner

Solution isn't good enough, but maybe you will do in your own way :)
I did it for one of my previous project. So, I used JsonIgnore there.

But maybe you may use automapper, it can be more flexible. Or source generator.

[enkodellc]

@IgorMamushin I did find a way, I added a detach method for EF to reset the Key:

        //used when you use ShallowClone or DeepClone and need to get rid of the index
        public void Detach<T>(T entity) where T : class
        {
            Entry(entity).State = Microsoft.EntityFrameworkCore.EntityState.Detached;
        }

[enkodellc]

@IgorMamushin you should submit your code as a PR

[IgorMamushin]

Ya, i don't think that it's a good solution anyway.

Maybe i will find time for do it well