client-Side:

<script type="text/javascript">
        OnMapCreating = function () {
            OpenLayers.Control.MousePosition.prototype.displayProjection = new OpenLayers.Projection("EPSG:4326");

            OpenLayers.Control.MousePosition.prototype.formatOutput = function (lonLat) {

                lonLat = lonLat.transform(new OpenLayers.Projection("EPSG:900913"),
                                new OpenLayers.Projection("EPSG:4326"));


                var digits = parseInt(this.numdigits);
                var newHtml = '';
                if (this.showType == 'dms') {
                    newHtml = this.prefix
                + this.getDms(lonLat.lon.toFixed(digits))
                + ', '
                + this.getDms(lonLat.lat.toFixed(digits))
                + this.suffix;
                } else if (this.showType == 'dmslatlon') {
                    newHtml = this.prefix
                + this.getDms(lonLat.lat.toFixed(digits))
                + ', '
                + this.getDms(lonLat.lon.toFixed(digits))
                + this.suffix;
                } else if (this.showType == 'lonlat') {
                    newHtml =
                this.prefix +
                lonLat.lon.toFixed(digits) +
                this.separator +
                lonLat.lat.toFixed(digits) +
                this.suffix;
                } else if (this.showType == 'latlon') {
                    newHtml =
                this.prefix +
                lonLat.lat.toFixed(digits) +
                this.separator +
                lonLat.lon.toFixed(digits) +
                this.suffix;
                }

                return newHtml;
            }
        }
    </script>



Server-Side:

 protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                LayerOverlay ov = new LayerOverlay();
                ov.Layers.Add(googleLayer);
                ov.IsBaseOverlay = true;

                InMemoryFeatureLayer inmlayer = new InMemoryFeatureLayer();
                inmlayer.InternalFeatures.Add(new Feature(0, 0));
                inmlayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
                inmlayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyles.Capital1;

                // = MouseCoordinateType.DegreesMinutesSeconds;

                Map1.MapBackground.BackgroundBrush = new GeoSolidBrush(GeoColor.FromHtml("#E5E3DF"));
                Map1.MapUnit = GeographyUnit.Meter;


                LayerOverlay staticOverlay = new LayerOverlay();
                staticOverlay.IsBaseOverlay = false;
                staticOverlay.Layers.Add(inmlayer);

                Map1.MapTools.MouseCoordinate.Enabled = true;
                Map1.MapTools.MouseCoordinate.MouseCoordinateType = MouseCoordinateType.DegreesMinutesSeconds;
                Map1.CurrentExtent = new RectangleShape(-1000000, 1000000, 1000000, -1000000);
                Map1.MapUnit = GeographyUnit.Meter;
                Map1.CustomOverlays.Add(ov);
                Map1.CustomOverlays.Add(staticOverlay);
            }
        }
        GoogleMapsLayer googleLayer = new GoogleMapsLayer();


        protected void Button1_Click(object sender, EventArgs e)
        {
            (((Map1.CustomOverlays[0] as LayerOverlay).Layers[0]) as GoogleMapsLayer).MapType= GoogleMapsMapType.RoadMap;
        }

        protected void Button2_Click(object sender, EventArgs e)
        {
            (((Map1.CustomOverlays[0] as LayerOverlay).Layers[0]) as GoogleMapsLayer).MapType = GoogleMapsMapType.Satellite;
        }

        protected void Button3_Click(object sender, EventArgs e)
        {
            (((Map1.CustomOverlays[0] as LayerOverlay).Layers[0]) as GoogleMapsLayer).MapType = GoogleMapsMapType.Hybrid;
        }