From the October 2008 Issue of Prestwood eMag

Prism Delphi for .Net Archive: ASP.NET under Delphi By Joshua Delahunty

Posted 7 years ago on 5/3/2006 and updated 1/20/2009 Take Away: use of Sender under Delphi for .NET

Let's say you have a DropDownList object on your ASP.NET form, and you want to access the Items property without actually naming the object.  You can do this the same way you would with a Win32 application under Delphi.

The following code will capture the currently selected string each time it changes in the drop-down (note that, under ASP.NET, this only occurs when some reason exists for a "trip to the server", and the user choosing a new drop-down value is NOT such a reason (at least, not when runat="server" is set)).

This assumes the default naming of DropDownList1 for the object:

procedure TWebForm1.DropDownList1_SelectedIndexChanged(sender: System.Object; e: System.EventArgs);
begin
    sItemString := DropDownList(sender).Items.Item[DropDownList(sender).SelectedIndex].ToString;
end;

(we are simply casting the sender argument as a DropDownList, since sender is the object that caused the event, and it's a DropDownList, but we need to "upcast" from Object in order to access the DropDownList properties). 

This makes this code portable to other DropDownLists, regardless of their naming or scoping.

Comments

KB Post Contributed By Joshua Delahunty:

I am a software engineer with many years professional experience, using everything from 6809 assembly language to C, C++, Delphi, Paradox for Windows, and Borland JBuilder.