调用可以很灵活，代码如下：

using System;
using System.Configuration;
using System.Web;
using System.Web.UI;
using System.Text;
using System.IO;namespace aspnet_test
{
    /// <summary>
    /// 单个文件上传类
    /// 
    /// 可以自定义：上传目录，上传文件类型、大小，是否使用随机上传文件名。
    /// 
    /// 作者：laifangsong  QQ：25313644  GMail:laifangsong@gmail.com
    /// 原文：http://www.cnblogs.com/jiny-z/archive/2007/05/30/764762.html
    /// </summary>
    public class UploadFile_Single
    {
        /* web.config设置：
         * <appSettings>        
         *     <add key="uploadDir" value="UploadFiles/" />
         *   <add key="uploadFileExt" value="gif|jpg|jpeg|png|bmp|doc|xls|hlp|chm|rar|zip" />    
         *   <add key="uploadFileSize" value="2048" />
         *   <add key="isUseRandFileName" value="true" />            
         * </appSettings>
         * 
         * private string uploadDir = ConfigurationSettings.AppSettings["uploadDir"];;
         * private string uploadFileExt = ConfigurationSettings.AppSettings["uploadFileExt"];
         * private int uploadFileSize = int.Parse(ConfigurationSettings.AppSettings["uploadFileExt"]);
         * private bool isUseRandFileName = bool.Parse(ConfigurationSettings.AppSettings["uploadFileExt"]);
         * *///上传目录，相对于本文件路径；以“/”结尾；如果目录不存在，会自动创建；如果要启用绝对路径，写法:“/虚拟目录名称/上传文件目录名称/”
        private string uploadDir = "UploadFiles/";
        //允许上传文件类型，逗号隔开
        private string uploadFileExt = "gif|jpg|jpeg|png|bmp|doc|xls|hlp|chm|rar|zip";
        //允许上传文件大小，k 为单位
        private int uploadFileSize = 2048;
        //是否使用随机上传文件名；如果不使用，会覆盖上传目录的同名文件
        private bool isUseRandFileName = true;//上传结果
        private string uploadResult = "";
        //上传文件保存路径
        private string uploadPath = "";
        
        public string UploadDir
        {
            get
            {
                return uploadDir;
            }
            set
            {
                uploadDir = value;
            }
        }
        public string UploadFileExt
        {
            get
            {
                return uploadFileExt;
            }
            set
            {
                uploadFileExt = value;
            }
        }
        public int UploadFileSize
        {
            get
            {
                return uploadFileSize;
            }
            set
            {
                uploadFileSize = value;
            }
        }
        public bool IsUseRandFileName
        {
            get
            {
                return isUseRandFileName;
            }
            set
            {
                isUseRandFileName = value;
            }
        }
        public string UploadResult
        {
            get
            {
                return uploadResult;
            }
        }
        public string UploadPath
        {
            get
            {
                return uploadPath;
            }
        }        //上传文件方法
        public bool Upload(Page page)
        {
            HttpPostedFile uploadFile = page.Request.Files[0];
            //获取上传文件属性
            string fileFullName = uploadFile.FileName;
            string contentType = uploadFile.ContentType;
            int contentLength = uploadFile.ContentLength;
            //取得文件名
            string fileName = System.IO.Path.GetFileName(fileFullName);
            //取得扩展名
            string fileExt = System.IO.Path.GetExtension(fileName).Remove(0, 1);
            //检测文件类型
            if( ("|"+UploadFileExt+"|").IndexOf( ("|"+fileExt+"|") ) < 0 )
            {
                uploadResult = "<font color='red'><b>上传文件格式错误！允许上传文件类型（" + uploadFileExt + "）</b></font>";
                return false;
            }
            //检测文件大小
            if(contentLength<1 || contentLength>uploadFileSize*1024)
            {
                uploadResult = "<font color='red'><b>上传文件大小错误！最大允许上传 " + uploadFileSize + " KB</b></font>";
                return false;                
            }
            //如果上传目录不存在，创建目录
            if(!uploadDir.EndsWith("/")) uploadDir += "/";
            string tempPath = "";
            string tempMapPath = "";
            string tempDir = uploadDir.Substring(0,1)!="/" ? uploadDir : uploadDir.Substring(uploadDir.IndexOf("/", 2)+1) ;
            while(tempDir.IndexOf("/")>=0)
            {
                tempPath += tempDir.Substring(0, tempDir.IndexOf("/")+1);            
                tempMapPath =  System.Web.HttpContext.Current.Server.MapPath(tempPath);
                if(!Directory.Exists(tempMapPath))
                {
                    Directory.CreateDirectory(tempMapPath);
                }
                tempDir = tempDir.Substring(tempDir.IndexOf("/")+1);
            }
            //随机文件名
            if(isUseRandFileName)
            {
                fileName = DateTime.Now.ToString("yyyyMMddhhmmss") + (new Random()).Next(100, 1000).ToString() + "." + fileExt;
            }string saveFilePath =  System.Web.HttpContext.Current.Server.MapPath(uploadDir) + @"\" + fileName;            
            uploadFile.SaveAs(saveFilePath);

            uploadPath 

string sql = "update table 1 set f_uploadpath='" & uploadPath & "' where ";
            

调用：

UploadFile_Single upfile = new UploadFile_Single();
upfile.Upload(this);

            UploadFile_Single upfile = new UploadFile_Single();
            upfile.UploadDir = "UploadFiles/";
            upfile.UploadFileExt = "gif|jpg|jpeg|png|bmp";
            upfile.UploadFileSize = 1024;
            upfile.IsUseRandFileName = true;
            upfile.Upload(this);

            UploadFile_Single upfile = new UploadFile_Single();
            upfile.UploadDir = "/虚拟目录名称/UploadFiles/1/2/3/";
            upfile.UploadFileExt = "gif|jpg|jpeg|png|bmp";
            upfile.UploadFileSize = 1024;
            upfile.IsUseRandFileName = true;
            upfile.Upload(this);
               
               Response.Write(upfile.UploadResult); //上传结果信息
               Response.Write(upfile.UploadPath); //上传保存路径

(上传目录可以用绝对路径，也可用相对路径；如果上传目录不存在，会自动创建)