// ......
 TextAdornmentLayer textAdornmentLayer = new TextAdornmentLayer(bitmap.Width / 2, 10);
 mapEngine.AdornmentLayers.Add(textAdornmentLayer);
// ......


  class TextAdornmentLayer : AdornmentLayer
    {
        ScreenPointF screenPointToDraw = new ScreenPointF();
        string strLogo = "My Own Logo";

        public TextAdornmentLayer(float screenPointToDrawX, float screenPointToDrawY)
            : base()
        {
            this.screenPointToDraw = new ScreenPointF(screenPointToDrawX, screenPointToDrawY);
        }

        protected override void DrawCore(GeoCanvas canvas, GeographyUnit mapUnit, Collection<SimpleCandidate> labelsInAllLayers)
        {
            //Draw Text
            GeoFont geoFont = new GeoFont("Arial", 10);
            canvas.DrawTextWithScreenCoordinate(strLogo, geoFont, new GeoSolidBrush(GeoColor.StandardColors.Blue), screenPointToDraw.X, screenPointToDraw.Y, DrawingLevel.LevelTwo);
            DrawingRectangleF drawingRectangleF = canvas.MeasureText(strLogo, geoFont);

            //// Draw Rectangle.
            canvas.DrawArea(
                GetScreenPointFs(drawingRectangleF), 
                new GeoPen(GeoColor.StandardColors.White, 2), 
                new GeoSolidBrush(GeoColor.StandardColors.Transparent), 
                DrawingLevel.LevelThree, 
                0, 0, PenBrushDrawingOrder.PenFirst);
        }

        private Collection<ScreenPointF[]> GetScreenPointFs(DrawingRectangleF drawingRectangleF)
        {
            ScreenPointF[] screenPointFs = new ScreenPointF[4];
            screenPointFs[0] = new ScreenPointF(screenPointToDraw.X - drawingRectangleF.Width / 2, screenPointToDraw.Y + drawingRectangleF.Height / 2);
            screenPointFs[1] = new ScreenPointF(screenPointToDraw.X + drawingRectangleF.Width / 2, screenPointToDraw.Y + drawingRectangleF.Height / 2);
            screenPointFs[2] = new ScreenPointF(screenPointToDraw.X + drawingRectangleF.Width / 2, screenPointToDraw.Y - drawingRectangleF.Height / 2);
            screenPointFs[3] = new ScreenPointF(screenPointToDraw.X - drawingRectangleF.Width / 2, screenPointToDraw.Y - drawingRectangleF.Height / 2);

            Collection<ScreenPointF[]> result = new Collection<ScreenPointF[]>();
            result.Add(screenPointFs);
            return result;
        }
    } 