ASP.NET FormView DetailsView and polymorphism

Question

I'm writing an ASP.NET Master Page that does the common grunt work for master/detail editing (ValidationSummary, error handling, popup of detail view using jQuery-ui dialog). It has two ContentPlaceHolder controls for the master and detail views, the master placeholder is expected to contain a GridView , and the detail placeholder either a DetailsView or a FormView .

The master page just needs to access a few basic members of the DetailsView or FormView:

• ChangeMode method
• DataBind method
• CurrentMode property
• InsertItem method
• UpdateItem method

I was surprised to see that, while both DetailsView and FormView have these same members, they are not (except DataBind) inherited from a common base class or interface. There are even two equivalent enums FormViewMode and DetailsViewMode , so that the ChangeMode and CurrentMode members don't even have the same signature.

I am intending to get round this by creating a wrapper class, but can anyone explain why they are implemented like this? Am I storing up trouble by attempting to use them polymorphically?

I find it hard to believe that this was not deliberate on the part of Microsoft's engineers, so I can only conclude that they intended to discourage polymorphic use.

Answer 1

while both DetailsView and FormView have these same members, they are not inherited from a common base class or interface.

Yes they are:

DetailsView : CompositeDataBoundControl, IDataItemContainer, INamingContainer, ICallbackContainer, ICallbackEventHandler, IPostBackEventHandler, IPostBackContainer, IDataBoundItemControl, IDataBoundControl, IFieldControl

FormView : CompositeDataBoundControl, IDataItemContainer, INamingContainer, IPostBackEventHandler, IPostBackContainer, IDataBoundItemControl, IDataBoundControl, IRenderOuterTableControl