arcmap - Creating new legend using ArcObjects?

I am trying to add simple legend to the map.

I wrote some simple test code below to see what happens but it did not work.

var map = activeView.FocusMap;

            IGraphicsContainer graphicsContainer = activeView.GraphicsContainer;
            IMapFrame mapFrame = graphicsContainer.FindFrame(map) as IMapFrame;
            UID uid = new UID();
            uid.Value = "esriCarto.Legend";
            IMapSurround mapSurround = map.CreateMapSurround(uid, null);
mapFrame.CreateSurroundFrame(uid, null);


            var legend = (ILegend)mapSurround;

            var legendItem = new VerticalLegendItemClass();
            legendItem.HeadingSymbol.Text = "served";
            legend.AddItem(legendItem);

            var legendItema = new VerticalLegendItemClass();
            legendItema.HeadingSymbol.Text = "unserved";
            legend.AddItem(legendItema);



            IElement element = legend as IElement;
            element.Geometry = envelope as IGeometry;
            graphicsContainer.AddElement(element, 0);

            activeView.Refresh();

The legend I am after, must be similar to this:

Can anyone assist?