Regression in 1.1 model binding for model types without default constructor

[Tragetaschen]

In 1.1, the ComplexTypeModelBinderProvider started to check for a default constructer: d09e921. This breaks my application.

I'm using a controller that calls TryUpdateModelAsync with a preconstructed IValueProvider and model instances:

await TryUpdateModelAsync(
    model,
    model.GetType(),
    prefix,
    valueProvider,
    a => true
);

Some of the model types don't have default constructors, most notably because I need some external dependencies for IValidatableObject. These model types now don't work anymore and my entire controller action fails.

The above commit doesn't really contain any information why this change was introduced and the binder itself doesn't require a default contsructor when the model object is pre-constructed

[Tragetaschen]

As a workaround, I have added a default constructor to the model types throwing a NIE.

[rynowak]

/cc @dougbu @Eilon - this might be patch worthy

IIRC we did this to try and improve the error message when a non-constructible type was used with CTMB. It would seem we regressed TryUpdateModel which uses the same infrastructure.

[dougbu]

Some of the background here can be found in issue #4895. @kichalla fixed that bug in PR #5368.

I agree the check for a parameterless constructor should be moved from ComplexTypeModelBinderProvider to ComplexTypeModelBinder and be done only when bindingContext.Model == null.

Nit: CanCreateModel() is a horribad name for a method which primarily checks whether value provider data is available for properties in the model. Might want to clean that up when adding a check that's actually about the ability to create the model.

[Eilon]

We will try to get this fixed in the patch.

[Eilon]

This patch bug is approved. Please use the normal code review process w/ a PR and make sure the fix is in the correct branch, then close the bug and mark it as done.

[Eilon]

@kichalla FYI this is an approved patch bug on your plate.

[Eilon]

Done?

[kichalla]

Sorry yeah done.

[Tragetaschen]

Yay!