Adds a new property, FieldName, to ModelBindingContext. The FieldName is
the name of whatever code-element is being bound, regardless of what
model-prefix is in use.
This is needed for cases like the Header model binder. We always want to
use the property/parameter name and we don't care about model prefixes.
- #2793
- add `ICollectionModelBinder`, allowing `GenericModelBinder` to call `CreateEmptyCollection()`
- adjust `CollectionModelBinder` and `DictionaryModelBinder` to activate model if default types are incompatible
- do not create default (empty) top-level collection in fallback case if Model already non-`null`
- change type checks in `GenericModelBinder` to align with `CollectionModelBinder` capabilities
- add special case for `IEnumerable<T>`
- correct `ModelMetadata` of a few tests that previously did not need that information
- #1418
- add new fallback binding in `DictionaryModelBinder`
- similar to MVC 5 approach but more explicit and with better key conversion support
- fix bugs in `PrefixContainer` encountered while adding new tests of #1418 scenarios
- did not handle entries like "[key]" or "prefix.key[index]" correctly
- refactor part of `GetKeyFromEmptyPrefix()` into `IndexOfDelimiter()`; share with `GetKeyFromNonEmptyPrefix()`
- extend `ReadableStringCollectionValueProviderTest` to cover bracketed key segments
nits:
- remove use of "foo", "bar", and "baz" in affected test classes
- `""` -> `string.Empty`
- `vpResult` -> `result`
This change treats 'top-level' collection-type models similarly to
top-level POCO model - namely that they will always be instantiated even
if there's no data to put inside.