.NET Windows Forms in a Nutshell

Unified Event Handling

The majority of toolbar buttons act as shortcuts to menu items, so it makes sense to handle equivalent clicks with a single event handler. Unfortunately, Windows Forms does not provide a direct way of doing this. However, it is fairly easy to arrange such a scheme. We can write an event handler for the toolbar that locates the appropriate menu item and then calls its event handler.

All we need is some way of associating toolbar buttons with menu items. For this, we can use a class provided by the .NET Framework class libraries called System.Collections.Hashtable—it is designed to store associations between objects. We can use this to remember which toolbar buttons are equivalent to which menu items. Although the Designer cannot store these associations in a hash table for you automatically, it only requires a small amount of code in your form’s constructor. The following is the necessary C# code:

// Hashtable to associate buttons with menu items

private Hashtable toolbarButtonToMenu;

public MyForm()

{

    InitializeComponent();



    // Create hash table

    toolbarButtonToMenu = new Hashtable();



    // Associate ToolBarButtons with MenuItems

    toolbarButtonToMenu(toolBarFileNew)    = menuFileNew;

    toolbarButtonToMenu(toolBarFileOpen)   = menuFileOpen;

    toolbarButtonToMenu(toolBarEditCopy)   = menuEditCopy;

    toolbarButtonToMenu(toolBarEditCut)    = menuEditCut;

    toolbarButtonToMenu(toolBarEditPaste)  = menuEditPaste;

    toolbarButtonToMenu(toolBarEditDelete) = menuEditDelete;

}

The following ...