asp.net上传图片并同时生成缩略图

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
public partial class slt_Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void bt_upload_Click(object sender, 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(".") + "/image/" + "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(".") + "/image/" + "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();
        }
    }

}