A Command or DropDownBox on a toolbar typically needs an action to occur on the server. Examples are zooming the map or performing a query. The command or drop-down box specifies a ServerActionClass that contains its server-side action. This class implements the IServerAction interface, which requires a method called ServerAction (actually the command or drop-downbox implements an interface, such as IMapServerCommandAction, that in turn implements IServerAction and that also has specific functionality for the type of action).

A ToolbarItemInfo object is passed as the argument to the ServerAction method. This object allows the server-side action to obtain information about the toolbar item that was clicked on the client. The information also allows finding the Map or PageLayout to which the toolbar was buddied. The properties of the ToolbarItemInfo object are:

• the Name of the item on the toolbar
• a reference to the Toolbar to which the item belongs
• the web controls buddied to the toolbar, usually a Map or PageLayout

System.Object
   ESRI.ArcGIS.ADF.Web.UI.WebControls.Tools.ToolbarItemInfo

Reference