Controller-Side:

  public ActionResult AddAClickEvent()
        {
            Map map = new Map("Map1", new System.Web.UI.WebControls.Unit(100, System.Web.UI.WebControls.UnitType.Percentage), 510);
            map.MapBackground.BackgroundBrush = new GeoSolidBrush(GeoColor.FromHtml("#E5E3DF"));
            map.CurrentExtent = new RectangleShape(-125, 72, 50, -46);
            map.MapUnit = GeographyUnit.DecimalDegree;

            InMemoryFeatureLayer inmLayer = new InMemoryFeatureLayer();
            inmLayer.InternalFeatures.Add(new Feature(0, 0));
            inmLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
            inmLayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyles.Capital1;
            
            LayerOverlay layeroverlay = new LayerOverlay("MarkerOverlay");
            layeroverlay.Layers.Add("name", inmLayer);

            map.CustomOverlays.Add(layeroverlay);
            return View(map);
        }

        [MapActionFilter]
        public void ClickEvent(Map map, GeoCollection<object> args)
        {
            (((LayerOverlay)map.CustomOverlays["MarkerOverlay"]).Layers["name"] as InMemoryFeatureLayer).InternalFeatures.Clear();
        }


View-Side:

@using ThinkGeo.MapSuite.Core;
@using ThinkGeo.MapSuite.MvcEdition;
@model ThinkGeo.MapSuite.MvcEdition.Map 
<script language="javascript" type="text/javascript">
    function mapClick(e) {
        var params = { x: e.worldXY.lon, y: e.worldXY.lat };

        Map1.ajaxCallAction('@ViewContext.RouteData.Values["Controller"].ToString()', 'ClickEvent', params, mapCallback);
    }

    function mapCallback(result) {
        var layer = Map1.getLayer("MarkerOverlay");
        layer.redraw(true);
    }
</script>
<div class="four columns" id="navigation">
    @{Html.RenderPartial("SourceCode");}
    <div id="instrux-body">
        <div id="instrux-text">
            Click on the map to add a marker.
        </div>
    </div>
</div>
<div class="twelve columns" id="main">
    <div>
        @{
            Html.ThinkGeo().Map(Model)
                .OnClientClick("mapClick").Render();
        }
    </div>
</div>