Get the geometry from the lasso selection tool

Question

I'm building an Add-in solution in ArcGIS 10 that contains a custom tool. I'd like to borrow the functionality of the lasso selection tool without reinventing the wheel. Is there a way to intercept the geometry of the lasso selection area from the mouse up event? I want to pass the geometry of the lasso area to a spatial filter.

I know how to get control of the lasso tool with the following code in my custom tool class:

private ITool m_SelectTool;
protected override void OnActivate()
        {         
            UID uid = new UID();
            uid.Value = "esriArcMapUI.SelectByLassoTool";
            ICommandItem commandItem = ArcMap.Application.Document.CommandBars.Find(uid, false, false);
            ICommand command = commandItem.Command;
            m_SelectTool  = (ITool)command;            
        }

Answer 1

I don't think this is possible (intercepting another tool's private data/events), but the good news is that reinventing the wheel is pretty easy when the inventor shows you how to do it.

See the Custom selection extension Add-In Sample, particularly the SelectByLineTool class. You could tweak it to use a NewPolygonFeedback instead of a line feedback, and add points to it in OnMouseMove instead of OnMouseDown, and Stop the feedback in OnMouseDown instead of OnDoubleClick.

Answer 2

Here is the code used in my solution based on modifying the Esri custom selection extension Add-in sample:

private bool m_isMouseDown = false;
private ESRI.ArcGIS.Display.INewPolygonFeedback m_polyFeedback;
private IActiveView m_focusMap;

protected override void OnMouseDown(MouseEventArgs arg) 
{
    IMxDocument mxDoc = ArcMap.Document;
    m_focusMap = mxDoc.FocusMap as IActiveView;
    IPoint point = m_focusMap.ScreenDisplay.DisplayTransformation.ToMapPoint(arg.X, arg.Y) as IPoint;

    if (m_polyFeedback == null)
    {
        m_polyFeedback = new ESRI.ArcGIS.Display.NewPolygonFeedback();
        m_polyFeedback.Display = m_focusMap.ScreenDisplay;
        m_polyFeedback.Start(point);
    }
    else
    {
        m_polyFeedback.AddPoint(point);
    }

    m_isMouseDown = true;

}
protected override void OnMouseMove(MouseEventArgs arg)
{
    if (!m_isMouseDown) return;

    IMxDocument mxDoc = ArcMap.Document;
    m_focusMap = mxDoc.FocusMap as IActiveView;
    IPoint point = m_focusMap.ScreenDisplay.DisplayTransformation.ToMapPoint(arg.X, arg.Y) as IPoint;

    if (m_polyFeedback == null)
    {
        m_polyFeedback = new ESRI.ArcGIS.Display.NewPolygonFeedback();
        m_polyFeedback.Display = m_focusMap.ScreenDisplay;
        m_polyFeedback.Start(point);
    }
    else
    {
        m_polyFeedback.AddPoint(point);
    }

}
protected override void OnMouseUp(MouseEventArgs arg)
{

    if (!m_isMouseDown) return;

    IPolygon polygon = m_polyFeedback.Stop();

    //Do something with the polygon here

    m_isMouseDown = false;
    m_polyFeedback = null;
}