Updating UI objects in windows forms
- by P a u l
Pre .net I was using MFC, ON_UPDATE_COMMAND_UI, and the CCmdUI class to update the state of my windows UI.
From the older MFC/Win32 reference:
Typically, menu items and toolbar buttons have more than one state. For
example, a menu item is grayed
(dimmed) if it is unavailable in the
present context. Menu items can also
be checked or unchecked. A toolbar
button can also be disabled if
unavailable, or it can be checked.
Who updates the state of these items
as program conditions change?
Logically, if a menu item generates a
command that is handled by, say, a
document, it makes sense to have the
document update the menu item. The
document probably contains the
information on which the update is
based.
If a command has multiple
user-interface objects (perhaps a menu
item and a toolbar button), both are
routed to the same handler function.
This encapsulates your user-interface
update code for all of the equivalent
user-interface objects in a single
place.
The framework provides a convenient
interface for automatically updating
user-interface objects. You can choose
to do the updating in some other way,
but the interface provided is
efficient and easy to use.
What is the guidance for .net Windows Forms? I am using an Application.Idle handler in the main form but am not sure this is the best way to do this. About the time I put all my UI updates in the Idle event handler my app started to show some performance problems, and I don't have the metrics to track this down yet. Not sure if it's related.
