Common bindable interface

Question

What it makes that collections are bindable? Is there common interface for List, DataTable with can bind to same control?

Answer 1

To explain how List<T> and DataTable work (the footnote of the question), read the following but noting that:

• List<T> implements IList and has a public T this[int index] {get;} which is used for resolving metadata
• DataTable implements IListSource, which provides the table's default DataView; the DataView implements IList, and implements ITypedList to provide metadata

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Collections bind in the following order:

• the source is tested for IListSource; if available the IList is obtained via GetList()
• otherwise the source is tested for IList; if unavailable an exception is thrown

then metadata for the IList is queried:

• the IList is tested for ITypedList; if available this is used via GetProperties
• the IList is tested for a public typed (non-object) indexer, i.e. public Foo this[int index] { get; } - if found, Foo is implied as the type and metadata obtained via TypeDescriptor.GetProperties(Type)
• else the first item (if non-empty) is queried via GetType() for the type, and metadata obtained via TypeDescriptor.GetProperties(Type)

we now have access to the items (IList) and their metadata; additional support (optional) is provided via IBindingList (provides 2-way binding and basic sorting etc), IBindingListView (provides advanced sorting, filtering, etc), ICancelAddNew and IRaiseItemChangedEvents.

For most common scenarios (show data and push changes back) List<T> is fine; if you need to show unrelated updates as they happen BindingList<T> helps - but note that to support member level updates (as opposed to just add/remove/etc) the T must implement INotifyPropertyChanged

For reference, "metadata" here means "a set of PropertyDescriptors" (1 per column/property), which provide access to the underlying data (when supplied with an object), and information about the member itself (name, type, etc).