Handling partial updates (under-posting) with AutoMapper

Question

I'm trying to find a method of handling partial updates; A ViewModel has 5 fields, but only one field is sent in the Request (i.e. only send fields that were modified instead of posing the entire view model), since null values were not explicitly sent for the other fields, I don't think that they should be set to null. Since AutoMapper does not have any kind of support for a Bind list, it's proving difficult to find an elegant solution...

public virtual IActionResult Edit(int id, ViewModel1 viewModel)
{
  var model = GetModel(id);
  mapper.Map(viewModel, model);
  // any field that was not posted, but exists in the ViewModel1 is now null in the model
  ...
}

The only approach I can think of, is to use Request.Form.Keys and Reflection to build an ExpandoObject that only contains the posted properties, then set CreateMissingTypeMaps and ValidateInlineMaps to allow AutoMapper to map the dynamic types... It just feels like this is a dirty workaround to compensate for functionality that's missing in AutoMapper... Is there a standard way of handling this?

https://stackoverflow.com/questions/43947475/how-to-ignore-null-values-for-all-source-members-during-mapping-in-automapper-6 — RichardMc, May 02 '19 at 16:35
I don't want to ignore null values if they were explicitly posted. — Failwyn, May 02 '19 at 16:38
Dynamic object mapping has no connection whatsoever with inline maps. It will just work. — Lucian Bargaoanu, May 02 '19 at 16:44
I was getting an error before I added that, I'll check it again, but it doesn't have any impact on the question. — Failwyn, May 02 '19 at 16:48
You can try [conditions](http://docs.automapper.org/en/latest/Conditional-mapping.html). — Lucian Bargaoanu, May 03 '19 at 04:07
Directly mapping from a dictionary would work too, no Expando needed, but the keys would have to match. — Lucian Bargaoanu, May 03 '19 at 04:36

Handling partial updates (under-posting) with AutoMapper

0 Answers0