ArcObjects Library Reference (Controls)

CommandPool CoClass

A collection of commands used by the ToolbarControl.

Product Availability

Available with ArcGIS Engine.

Description

The CommandPool is used for managing the collection of commands used by the ToolbarControl, a ToolbarMenu, a ToolbarPalette, or the commands shared between several ToolbarControl's. The ToolbarControl manages its CommandPool itself in order to maintain its command items. If a ToolbarMenu or ToolbarPalette are added to a ToolbarControl they will automatically share the same CommandPool as the ToolbarControl. If a ToolbarMenu or ToolbarPalette are used standalone they will mange their own CommandPool.

Extended Error Information

Use the ISupportErrorInfo method InterfaceSupportsErrorInfo to determine if the object supports extended error information. If the object supports extended error info, VC++ developers should use the OLE/COM IErrorInfo interface to access the ErrorInfo object. Visual Basic developers should use the global error object Err to retrieve this extended error information.

Interfaces

Interfaces	Description
ICommandPool	Provides access to the contents of the command pool.
ICommandPool2	Provides access to the contents of the command pool.
ICommandPoolEdit	Provides access to members that control the command pool.
ISupportErrorInfo	Indicates whether a specific interface can return Automation error objects.

Remarks

The CommandPool is used for managing the collection of Command objects (including Tool and ToolControl objects) objects used by the ToolbarControl. Normally, the CommandPool is entirely managed by the ToolbarControl, a ToolbarMenu or a ToolbarPalette in order to maintain to its command items.

The main job of the CommandPool is to create Command objects from valid UID's and prevent multiple instances of the same Command being created. This ensures that if the same Command is added to multiple ToolbarControl's, there will be only one actual instance of that Command in the CommandPool. When a Command is added by passing the ICommandPoolEdit::AddCommand method a valid UID, the first time that UID is supplied, a brand new Command is created and the CommandPool gives this a UsageCount of 1. If another ToolbarControl passes the ICommandPoolEdit::AddCommand the same UID the CommandPool will return the existing Command and will increment the UsageCount to 2.

By default each ToolbarControl has its own CommandPool. To ensure Commands are shared amongst multiple ToolbarControls the same CommandPool object must be set into each ToolbarControl. ToolbarMenu and ToolbarPalette objects also use a CommandPool. If a ToolbarMenu or ToolbarPalette is added to a ToolbarControl it will automatically share the same CommandPool as the ToolbarControl.

Other tasks performed by the CommandPool are:

Managing Command objects added by passing the ICommandPoolEdit::AddCommand method an ICommand. In such cases when the UID is missing the CommandPool will look for duplicate Commands.
Managing Command objects added by passing the ICommandPoolEdit::AddUID a valid UID with a SubType property set to 0, when the Command supports ICommandSubType. In such cases the CommandPool will create multiple Command objects for each available SubType.
The CommandPool passes each Command's OnCreate method a hook. The hook can be any object that implements an IDispatch interface, but is typically the ToolbarControl. The ICommandPool::Created property indicates whether ICommand::OnCreate has been called.