An instance of this class is created when a Tool has its ClientAction set to Circle, the user clicks on the Map or PageLayout, and the Tool's ServerActionClass is set to a class that implements IMapServerToolAction. The CircleEventArgs object is passed as the argument to the ServerAction method.

The CircleEventArgs will contain the center point and radius that defines the circle the user clicked. This circle may be used to do action on the server, such as querying the map or drawing graphics. Note the coordinates and radius of the circle are in screen pixels, and may need to be converted to map coordinates before using the circle.

System.Object
   System.EventArgs
      ESRI.ArcGIS.ADF.Web.UI.WebControls.ToolEventArgs
         ESRI.ArcGIS.ADF.Web.UI.WebControls.CircleEventArgs
            ESRI.ArcGIS.ADF.Web.UI.WebControls.MapCircleEventArgs

Reference