一般处理程序进行上传（修改后，中级版）

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form action="ProcessFileUp.ashx" method="post" enctype="multipart/form-data">
        <input type="file" name="fileup" />
        <input type="submit" value="上传" />
    </form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;

namespace CZBK.ItcastProject.WebApp._2015_5_27
{
    /// <summary>
    /// ProcessFileUp 的摘要说明
    /// </summary>
    public class ProcessFileUp : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/html";
            HttpPostedFile file= context.Request.Files[0];//获取上传的文件
            if (file.ContentLength>0)
            {
                //对上传的文件类型进行校验
                string fileName =Path.GetFileName(file.FileName);//获取上传文件的名称，包含扩展名
                string fileExt = Path.GetExtension(fileName);//获取用户上传的文件扩展名
                if (fileExt==".jpg")
                {
                    //对上传文件进行重命名
                    string newfileName = Guid.NewGuid().ToString();
                    //将上传的文件放在不同目录下
                    string dir = "/ImageUpload/"+DateTime.Now.Year+"/"+DateTime.Now.Month+"/"+DateTime.Now.Day+"/";
                    //创建文件夹
                    if (!Directory.Exists(context.Request.MapPath(dir)))
                    {
                        Directory.CreateDirectory(context.Request.MapPath(dir));
                    }
                    //文件的完整路径
                    string fullDir = dir + newfileName + fileExt;
                    //注意：保存一定要用context.Request.MapPath来回去路径
                    file.SaveAs(context.Request.MapPath(fullDir));
                    context.Response.Write("<html><body><img src='"+fullDir+"'></body></html>");
                    //file.SaveAs(context.Request.MapPath("/ImageUpload/"+fileName));//完成文件的保存
                    //context.Response.Write("<html><body><img src='/ImageUpload/" + fileName + "'></body></html>");
                }
                else
                {
                    context.Response.Write("只能上传图片文件");
                }
            }
            else
            {
                context.Response.Write("请选择上传文件");
            }
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}