public void CreateBitmapFromVisual(Window win, string fileName)
        {
            if (win == null || string.IsNullOrEmpty(fileName))
            {
                return;
            }

            int index = fileName.LastIndexOf(System.IO.Path.DirectorySeparatorChar);
            if (index > 0)
            {
                string tmpPath = fileName.Substring(0, index);
                if (!Directory.Exists(tmpPath))
                {
                    Directory.CreateDirectory(tmpPath);
                }
            }
          
            RenderTargetBitmap renderTarget = new RenderTargetBitmap((Int32)win.Width, ((Int32)win.Height), 96, 96, PixelFormats.Pbgra32);
            renderTarget.Render(win);
            PngBitmapEncoder bitmapEncoder = new PngBitmapEncoder();
            bitmapEncoder.Frames.Add(BitmapFrame.Create(renderTarget));
            using (Stream stm = File.Create(fileName))
            {
                bitmapEncoder.Save(stm);
            }
        }

 public void CreateBitmapFromVisual(Window win, string fileName)
        {
            if (win == null || string.IsNullOrEmpty(fileName))
            {
                return;
            }

            int index = fileName.LastIndexOf(System.IO.Path.DirectorySeparatorChar);
            if (index > 0)
            {
                string tmpPath = fileName.Substring(0, index);
                if (!Directory.Exists(tmpPath))
                {
                    Directory.CreateDirectory(tmpPath);
                }
            }

            System.Drawing.Graphics graphics = System.Drawing.Graphics.FromHwnd(IntPtr.Zero);
            float systemdpi = graphics.DpiX / 96;

            var bitmap = new System.Drawing.Bitmap((int) (win.Width* systemdpi), (int)(win.Height* systemdpi), System.Drawing.Imaging.PixelFormat.Format32bppArgb);

           using (System.Drawing.Graphics memoryGrahics = System.Drawing.Graphics.FromImage(bitmap))
            {
                memoryGrahics.CopyFromScreen((int)Math.Round(win.Left), (int)Math.Round(win.Top), 0, 0, new System.Drawing.Size((int)(win.Width* systemdpi), (int)(win.Height* systemdpi)), System.Drawing.CopyPixelOperation.SourceCopy);
            }

            bitmap.Save(fileName);            
        }