System.Web.UI.WebControls.Image imgFoto = new System.Web.UI.WebControls.Image();
System.Drawing.Image.GetThumbnailImageAbort myCallback = new     System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);
Bitmap myBitmap = new Bitmap("foto.jpg");
System.Drawing.Image myThumbnail = myBitmap.GetThumbnailImage(80, 80, myCallback, IntPtr.Zero);
imgFoto.ImageUrl = myThumbnail;