在ASP.NET中上传图片并生成缩略图

以下是引用片段：
private void btnUploadPicture_Click(object sender, System.EventArgs e)
{
   //检查上传文件的格式是否有效
   if(this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)
   {
    Response.Write("上传图片格式无效！");
    return;
   }

   //生成原图
   Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength];
   System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream;
   System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

   int oWidth = oImage.Width; //原图宽度
   int oHeight = oImage.Height; //原图高度
   int tWidth = 100; //设置缩略图初始宽度
   int tHeight = 100; //设置缩略图初始高度

   //按比例计算出缩略图的宽度和高度
   if(oWidth >= oHeight)
   {
    tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));
   }
   else
   {
    tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));
   }

   //生成缩略原图
   Bitmap tImage = new Bitmap(tWidth,tHeight);
   Graphics g = Graphics.FromImage(tImage);
   g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量插值法
   g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置高质量,低速度呈现平滑程度
   g.Clear(Color.Transparent); //清空画布并以透明背景色填充
   g.DrawImage(oImage,new Rectangle(0,0,tWidth,tHeight),new Rectangle(0,0,oWidth,oHeight),GraphicsUnit.Pixel);

   string oFullName = Server.MapPath(".") + "/" + "o" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存原图的物理路径
   string tFullName = Server.MapPath(".") + "/" + "t" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存缩略图的物理路径

   try
   {
    //以JPG格式保存图片
    oImage.Save(oFullName,System.Drawing.Imaging.ImageFormat.Jpeg);
    tImage.Save(tFullName,System.Drawing.Imaging.ImageFormat.Jpeg);
   }
   catch(Exception ex)
   {
    throw ex;
   }
   finally
   {
    //释放资源
    oImage.Dispose();
    g.Dispose();
    tImage.Dispose();
   }
}