Map into existing object

[robrich]

I'd like to be able to map into an existing object.

Use-case: I get the entity from the database, I have the model posted into the action. I don't want to replace the entity, just update those properties I got from the model.

Proposed:

public void MapToExistingDestination(this Source source, Destionation destination)
{
  destination.Name = source.Name;
  destination.Reason = source.Reason;
}

Then in my controller action (or service) I can have code like this:

[HttpPut("{id}")]
public ActionResult<Model> Put(int id, [FromBody]CustomerModel model)
{
  Customer customer = customerRepository.GetById(id);
  if (customer == null)
  {
    return NotFound();
  }
  model.MapToExistingCustomer(customer);
  customerRepository.Save(customer);
  return model;
}

[JasonBock]

This is something I'm considering with this issue. If it's done (I accept PRs ;) ), maybe the right thing to do is to generate a parameter of the destination type, rather than a Func<DestinationType> as you suggested.

[robrich]

Interesting. I can see value in both approaches. In my use-case I'm specifically copying properties between objects. In #12, the use-case is still creating a new one but overriding initialization. Are these use-cases different enough to justify API surface for each? Hm...