ActionLists for Windows.Forms

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• Download demo project - 40 Kb

Introduction

The .Net framework is really a nice framework, but as a programmer coming from the MFC world, I really miss some features like the ON_COMMAND/ON_UPDATE_COMMAND_UI mechanism.

This mechanism allows the decoupling of the UI and the code associated to it. It allows:

• to automatically share the code between menus, toolbars, buttons and other controls.
• to reduce the amount of code needed for updating the UI.
• to enable/disable controls according to conditions not related to the UI (for example a connection to a database).

Unfortunately, the ON_COMMAND/ON_UPDATE_COMMAND_UI mechanism is a message base mechanism which strongly relies on a specific message routing architecture. This mechanism can be reproduced in the .Net environment but it is far from being a pratical solution in a RAD environment. A nice alternative is the ActionList component provided by Delphi.

An ActionList is a collection of Actions. Each Action is itself a component associated to a given task. An Action provides the framework for:

• excuting the task in response to an UI event.
• enabling/disabling, checking/unchecking the controls related to the task according to some conditions.

Furthermore, this mechanism can be extended in order to:

• set the text of the controls.
• set the help text of the controls.
• show/hide the controls.
• set the icons associated to the controls.
• set the shortcut associated to the task.

Adding actions to your project

This a simple example based on the Find Dialog of the demo application. We will add an action wich will be associated to the Find button.

1. Open your dialog in Design Mode.
2. Add the components of the CDiese library to the Toolbox.
   
3. Drag an ActionList on the dialog
   
4. Edit the property Actions of the new ActionList. Add a new Action and set its properties.
   
5. Select the action in the component editor and add an EventHandler for the Execute and Update events.
   

   private void OnUpdateFind(object sender, System.EventArgs e)
   {
   	((CDiese.Actions.Action)sender).Enabled = _text.TextLength > 0;
   }
   

   private void OnFind(object sender, System.EventArgs e)
   {
   	RichTextBoxFinds mode = RichTextBoxFinds.None;
   
   	if (_bCase.Checked)
   	{
   		mode |= RichTextBoxFinds.MatchCase;
   	}
   	....
   	_RTF.Select(sel, _text.Text.Length);
   	_RTF.ScrollToCaret();
   }
   

6. Associate the action to the Find button
   

Latest updates

• 4th March 2002
  • First release

Serge .