asp.net上传图片

//检查上传文件的格式是否有效
        if (this.uploadfile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)
        {
            Response.Write("<script> alert('上传图片格式无效'); </script>");
            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 =800; //设置缩略图初始宽度  大于800自动取800
        int tHeight =1000); //设置缩略图初始高度 大于1000自动取1000


        //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 fullFileName = this.uploadfile.PostedFile.FileName.ToString();
        fullFileName = fullFileName.Remove(fullFileName.LastIndexOf('.'));
        string filename = fullFileName.Substring(fullFileName.LastIndexOf("\\") + 1);


         string strLocation = this.Server.MapPath(Page.Request.ApplicationPath) + "\\uploads\\"; //存储路径
           

        }


        Random r = new Random();                 //防止重名
        int i = (int)(r.NextDouble() * 10000);
        if (!Directory.Exists(strLocation))
        {
            Directory.CreateDirectory(strLocation);
        }



        //string oFullName =strLocation +"x"+i.ToString() + filename+".jpg"; //保存原图的物理路径
        string tFullName = strLocation + i.ToString() + filename + ".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();
        }
    }