System.Drawing.Bitmap.Save C# (CSharp) Method

        public void Save(Stream stream, ImageFormat format)
        {
            if (stream == null)
                throw new ArgumentNullException ("stream");

            if (NativeCGImage == null)
                throw new ObjectDisposedException ("cgimage");

            // for now we will just default this to png
            var typeIdentifier = "public.png";

            // Get the correct type identifier
            if (format == ImageFormat.Bmp)
                typeIdentifier = "com.microsoft.bmp";
            //			else if (format == ImageFormat.Emf)
            //				typeIdentifier = "image/emf";
            //			else if (format == ImageFormat.Exif)
            //				typeIdentifier = "image/exif";
            else if (format == ImageFormat.Gif)
                typeIdentifier = "com.compuserve.gif";
            else if (format == ImageFormat.Icon)
                typeIdentifier = "com.microsoft.ico";
            else if (format == ImageFormat.Jpeg)
                typeIdentifier = "public.jpeg";
            else if (format == ImageFormat.Png)
                typeIdentifier = "public.png";
            else if (format == ImageFormat.Tiff)
                typeIdentifier = "public.tiff";
            else if (format == ImageFormat.Wmf)
                typeIdentifier = "com.adobe.pdf";

            // Not sure what this is yet
            else if (format == ImageFormat.MemoryBmp)
                throw new NotImplementedException("ImageFormat.MemoryBmp not supported");

            using (var imageData = new NSMutableData ())
            {
                using (var dest = CGImageDestination.Create (imageData, typeIdentifier, frameCount))
                {
                    dest.AddImage (NativeCGImage, (NSDictionary)null);
                    dest.Close ();
                }

                using (var ms = new MemoryStream (imageData.ToArray()))
                {
                    ms.WriteTo (stream);
                    stream.Seek (0,System.IO.SeekOrigin.Begin);
                }
            }
        }

        private void RegisterCommands(ImagePresentationViewModel viewModel)
        {
            viewModel.SaveCommand = UICommand.Regular(() =>
            {
                var dialog = new SaveFileDialog
                {
                    Filter = "PNG Image|*.png|Bitmap Image|*.bmp",
                    InitialDirectory = Settings.Instance.DefaultPath
                };
                var dialogResult = dialog.ShowDialog();
                if (dialogResult.HasValue && dialogResult.Value)
                {
                    var tmp = viewModel.Image;
                    using (var bmp = new Bitmap(tmp))
                    {
                        if (File.Exists(dialog.FileName))
                        {
                            File.Delete(dialog.FileName);
                        }

                        switch (dialog.FilterIndex)
                        {
                            case 0:
                                bmp.Save(dialog.FileName, ImageFormat.Png);
                                break;
                            case 1:
                                bmp.Save(dialog.FileName, ImageFormat.Bmp);
                                break;
                        }
                    }
                }
            });
        }