Metafile scaling in WinForms

   public partial class MainForm : Form
   {
      public MainForm()
      {
         InitializeComponent();
      }

      private void MainForm_Paint(object sender, PaintEventArgs e)
      {
         var g = e.Graphics;
         var blueBrush = new SolidBrush(Color.Blue);
         var bluePen = new Pen(blueBrush);
         g.DrawRectangle(bluePen, 0, 0, 200, 200);
         g.DrawLine(bluePen, 100, 0, 100, 200);
         g.DrawLine(bluePen, 0, 100, 200, 100);
         g.DrawString(g.DpiX+" dpi", new Font("Arial", 10), blueBrush, 0, 205);

         Metafile metafile;
         MetafileHeader metafileHeader;
         var size = new Size(200, 200);
         using (var stream = new MemoryStream())
         {
            using (Graphics offScreenBufferGraphics = Graphics.FromHwndInternal(IntPtr.Zero))
            {
               IntPtr deviceContextHandle = offScreenBufferGraphics.GetHdc();
               metafile = new Metafile(stream, deviceContextHandle, new RectangleF(0, 0, size.Width, size.Height), MetafileFrameUnit.Millimeter, EmfType.EmfPlusOnly);
               offScreenBufferGraphics.ReleaseHdc();

               using (Graphics mg = Graphics.FromImage(metafile))
               {
                  mg.PageUnit = GraphicsUnit.Millimeter;
                  var redPen = new Pen(new SolidBrush(Color.Red));

                  // This is how to get the correct scale factor:
                  metafileHeader = metafile.GetMetafileHeader();
                  float sx = metafileHeader.DpiX/g.DpiX;
                  float sy = metafileHeader.DpiY/g.DpiY;
                  mg.ScaleTransform(sx, sy);

                  mg.DrawLine(redPen, 0, 0, 200, 200);
                  mg.DrawLine(redPen, 0, 200, 200, 0);
               }
            }
         }

         g.DrawImage(metafile, 0, 0, 200, 200);
         g.DrawString("metafile.Width: " + metafile.Width, new Font("Arial", 10), blueBrush, 0, 220);
         g.DrawString("metafileHeader.DpiX: " + metafileHeader.DpiX, new Font("Arial", 10), blueBrush, 0, 240);
      }

   }