ArcGIS Engine Developer Guide

BUILDING APPLICATIONS WITH WINDOWS CONTROLS
15. In the Class View window, navigate to the BaseCommand Enabled property
and right-click to display the context menu. Click Add, then Override to add
the property to the code window.
16. Add the following code to override the default Enabled value as implemented
by the BaseTool class.
The ICommand_OnCreate event is passed a
handle or hook to the application that the
command will work with. In this case it can be a
MapControl, PageLayoutControl, or
ToolbarControl. Rather than adding code into the
OnCreate event to determine the type of hook
that is being passed to the command, you will
use the HookHelper to handle this. A command
or tool needs to know how to handle the hook
it gets passed, so a check is needed to determine
the type of ArcGIS Control that has been
passed. The HookHelper is used to hold the hook
and return the ActiveView regardless of the type
of hook (in this case a MapControl,
PageLayoutControl, or ToolbarControl).
public override bool Enabled
{
get
{
// Set the enabled property.
if (m_HookHelper.ActiveView != null)
{
return true;
}
else
{
return false;
}
}
}
17. In the Class View window, navigate to the BaseTool OnMouseDown method
and right-click to display the context menu. Click Add, then Override to add
the property to the code window.
18. Add the following code to the override the default OnMouseDown functionality
as implemented by the BaseTool class.
public override void OnMouseDown(int Button, int Shift, int X, int Y)
{
base.OnMouseDown (Button, Shift, X, Y);
// Get the active view.
IActiveView activeView = m_HookHelper.ActiveView;
// Create a new text element.
ITextElement textElement = new TextElementClass();
// Create a text symbol.
ITextSymbol textSymbol = new TextSymbolClass();
textSymbol.Size = 25;
// Set the text element properties.
textElement.Symbol = textSymbol;
textElement.Text = DateTime.Now.ToShortDateString();
// QI for IElement.
IElement element = (IElement) textElement;
// Create a page point.
IPoint point = new PointClass();
point = activeView.ScreenDisplay.DisplayTransformation.ToMapPoint(X,Y);
Chapter 6 • Developer scenarios • 349