ICommand Interface

Provides access to members that define a COM command.

Product Availability

Description

All the commands that are built into the ArcCatalog and ArcMap applications are COM based commands. As a developer, you can create custom commands in development environments that support COM, i.e. Visual Basic, .Net (C# and VB.Net), or C++. COM based commands are distributed in the form of ActiveX DLLs. You can create the following types of commands:

• Buttons and menu items are the simplest types of commands. Buttons generally appear as icons on toolbars and menu items appear in menus. A simple action is performed when the button or menu item is clicked.
• Tools are similar to buttons but they also require interaction with the application's display. The Zoom In command is a good example of a tool--you click or drag a rectangle over a map before the display is redrawn to show the map contents in more detail.
• Tool controls are commands that act like comboboxes or editboxes. Comboboxes let you choose an option from a drop-down list. For example, in ArcMap, you can choose which layer(s) you are selecting features from when working with a map. Editboxes are editable textboxes where you can type in text.

When To Use

Use the ICommand interface to query the properties of a COM command or to create your own COM command.

When you are creating a new COM command, you must implement the ICommand interface in your class code. This interface determines the behavior and properties of simple commands such as buttons and menu items. For example, the ICommand interface sets command properties such as caption, name, category, bitmap, statusbar message, tooltip, help context id and help file, enabled state, and checked state. It also defines what action happens when the command is clicked.

Members

	All Properties Methods	Description
	Bitmap	The bitmap that is used as the icon on this command.
	Caption	The caption of this command.
	Category	The name of the category with which this command is associated.
	Checked	Indicates if this command is checked.
	Enabled	Indicates if this command is enabled.
	HelpContextID	The help context ID associated with this command.
	HelpFile	The name of the help file associated with this command.
	Message	The statusbar message for this command.
	Name	The name of this commmand.
	OnClick	Occurs when this command is clicked.
	OnCreate	Occurs when this command is created.
	Tooltip	The tooltip for this command.

CoClasses that implement ICommand

Remarks

Even if you do not have to write code for all the properties and methods on the ICommand interface to meet the requirements of your command design, you must at least create stub code for all of the properties and methods.

When you implement ICommand to create a custom command, you will find that your class constructor and destructor are called more than once per session.  Commands are constructed once initially to get information about them, like the name, bitmap, etc and then they are destroyed.  When the final, complete construction takes place, the OnCreate method gets called.  OnCreate gets called only once, so you can rely on it to perform initialization of member variables.  You can check for initialized member variables in the class destructor to find out if OnCreate has been called previously.

See Also

ITool Interface | IToolControl Interface | ICommandSubType Interface