ArcGIS Engine Developer Guide

.NET APPLICATION PROGRAMMING INTERFACE
To override any member, you can right-click the member of the base class in the
Solution Explorer window, click Add, then click Override to stub out the member
as overridden. Note that if you right-click the member of the underlying
interface (ICommand or ITool) instead of the base class member, the overridden
member will not include the overrides keyword, and the method will instead be
shadowed.
[VB.NET]
Public Overrides Sub OnClick()
' Your OnClick
End Sub
[C#]
public override void OnClick()
{
// Your OnClick
}
Alternatively, to override a member of the base class, click Overrides from the
dropdown list on the right in the Code Window Wizard bar, then choose the
member you want to override from the left dropdown list. This will stub out the
member as overridden.
What do the base classes do by default?
The table below shows the base class members that have a significant base class
implementation, along with a description of that implementation. Override these
members when the base class behavior is not consistent with your customization.
For example, Enabled is set to True by default; if you want your custom command
enabled only when a specific set of criteria has been met, you must override
this property in your derived class.
Member
ICommand::Bitmap
ICommand::Category
ICommand::Checked
ICommand::Enabled
ITool::OnContextMenu
ITool::Deactivate
Description
The given bitmap is made transparent based on the
pixel value at position 1,1. The bitmap is null until
set by the derived class.
If null, sets the category "Misc."
Set to False.
Set to True.
Set to False.
Set to True.
Working with the ESRI .NET component category classes
To help register .NET components in COM component categories, ESRI provides
the ESRI.ArcGIS.Utility.CATIDs namespace, which has classes that represent
each of the ArcGIS component categories. Each class knows its CATID and
exposes static methods (Register and Unregister) for adding and removing components.
Registering your component becomes as easy as adding COM registration
methods with the appropriate attributes and passing the received CLSID to the
appropriate static method.
The example below shows a custom Pan tool that registers itself in the ESRI Mx
Commands component category. Notice in this example that
Chapter 4 • Developer environments • 171