Some Dictionaries do not get model bound

[pranavkm]

Consider the model

public class Foo
{
    public Dictionary<string, string> Values { get; set; }
}

The name generated by Html.NameFor(v => v.Values["height"]) is Values[height] however this expression does not get model bound.

There's a gap in the collection model binder where it only attempts to bind numeric keys. The right fix for this would be to call into IEnumerableValueProvider and then bind each key and value independently and add the result to the dictionary.

[pranavkm]

cc @kichalla This issue seems to repro in WebAPI 2.3.2, so we might be able to port this fix back to WebAPI.

[danroth27]

@pranavkm What is the behavior in MVC 5?

[dougbu]

may also need to change @Html.NameFor() to get this working end-to-end. the name Values[height] is ambiguous, covering for example indexers using a variable named height. shouldn't the generated name be Values["height"] in this case?
since @Html.Namefor() defers naming of the indexer argument to Func<object, object>.ToString(), might not be simple to finish this scenario.

[rynowak]

See: RoundTrippedValues_GetsModelBound_ForStringIndexedProperties for a functional test that needs to be updated

[yishaigalatzer]

@pranavkm did you do the comparison to MVC5?

[kichalla]

Just FYI...I have tried in MVC 5 and it also didn't support this..

[dougbu]

what about Web API 3?

[kichalla]

Pranav and I investigated earlier(please take a look at the earlier comment in this bug) about this for 2.3.2 and it was not supported there too..

[danroth27]

Clearing milestone so we look at this again.

[Eilon]

We need to make sure we can model bind everything that our HTML helpers generate.

[dougbu]

I'm surprised to say MVC 5 supports binding to Dictionary<string, TValue> properties. It doesn't support for example Dictionary<int, string> but submitted values for such dictionaries are visible in ModelState. MVC 6 has regressed in both ways i.e. w.r.t. ModelState entries as well as model dictionary entries.

[dougbu]

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