private void axMapControl1_OnMouseDown(object sender, ESRI.ArcGIS.Controls.IMapControlEvents2_OnMouseDownEvent e)

{

ILineElement pLineElement;

 IActiveView pActiveView;

IRgbColor pRgbColor;

IRubberBand pRubberBand;

ISimpleLineSymbol pSimpleLineSymbol;

IPolyline pPloyline;

pActiveView = axMapControl1.ActiveView;

pSimpleLineSymbol = new SimpleLineSymbolClass();

pSimpleLineSymbol.Style = esriSimpleLineStyle.esriSLSSolid;

pRgbColor = new RgbColorClass();

pRgbColor.Red = 125;

pSimpleLineSymbol.Color = pRgbColor;

pRubberBand = new RubberLineClass();

pLineElement = new LineElementClass();

pLineElement.Symbol = pSimpleLineSymbol;

pPloyline = pRubberBand.TrackNew(pActiveView.ScreenDisplay, pSimpleLineSymbol as ISymbol) as IPolyline;

pElement = new LineElement();

pElement = pLineElement as IElement;

pElement.Geometry = pPloyline;

IGraphicsContainer pGraphicsContainer = axMapControl1.ActiveView.FocusMap as IGraphicsContainer;

pGraphicsContainer.AddElement(pElement, 0);

axMapControl1.ActiveView.Refresh();

}