Typed Dataset's validation and custom classes' collections

Typed Dataset's validation and custom classes' collections:


A. When use Custom Class: the key is the Custom collections:

(a) the best is to use IList and use AOP to support databinding (but I do not even know it is possible or not!)
---- “low tech hack”:
(i) use UI code to trigger refreshing when code-changing value in grid;
(ii) use bindingSource to sort, search (note: for sorting, the comparable is in the item class itself, not in the collection!)

(b) second choice: use IBindingList (it is .net build-in)

(c) third choice, use one or a few custom-made generic that expand IBindingList
(i) IBindingList needs to add search/sort (override AddNewCore etc.)
(ii) IBindingList is not enough, because collection’s AddNewCore need to add back-pointer to the object it adds. This is needed because ICancelAddNew is new in 20; some controls do not know to call it. (in CSLA, this is the reason for IEditableCollection).

(d) Use a lot of specific strongly typed collections: (the only positive): there is a visual thing: you cannot drag a generic collection. Since a generic collection is not “real” yet, so, it makes sense; however, why not use asp approach: use the returning collections from a façade method, or/and, ask user to fill in the parameter type of the generic collection – this is a good addin for visual studio. (low tech hack) to use the visual, you can simply put the closed generic collection in a dummy class.



B. When use DataSet, the key is the Validation Logic:

----Validation logic: because we do not want to rewrite the set/get methods in dataset, so, we need to use events. However, the validation must not depend on the UI level. We can use the exact same technique in CSLA to centralize it (or the “original” centralized, but just a big switch – it is fine also). By doing this, we can still do automated unit testing.



C. Other things in Databinding

---- we can use general ICustomTypeDescriptor and attributes to configure the public “columns”

---- In simple implementation, IEditableObject does not need to be recursive, because child collection means another grid, so, will EndEdit anyway.
----databinding all uses propertydescriptor (a way of reflection, but with extra indirect of this “interface” (TypeDescriptor, ListBindingHelper), so that we can use the same code for dataset and custom class). So, if we add “AddValueChanged”, the list will be notified. However, most code-change is via direct code, not reflection, so, must also use INotifyPropertyChanged