.net实现图片权限控制，对不同的帐户加水印(5)

 
从浏览器获取用户的session并判断是否登录。
 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using 图片权限控制.DataSetPicxsdTableAdapters;
using System.Web.SessionState;
using System.Drawing;
using System.Drawing.Imaging;
 
 
namespace 图片权限控制
{
    /// <summary>
    /// $codebehindclassname$ 的摘要说明
    /// </summary>
   
    public class DownLoad : IHttpHandler,IRequiresSessionState  //注意：需要实现这个接口
    {
 
        public void ProcessRequest(HttpContext context)
        {
          
            string filename=context.Request ["filename"];
            context.Response.ContentType = "image/JPEG";
            string UrlFile = HttpUtility.UrlEncode(filename);
            context.Response.AddHeader("Content-Disposition",string.Format ("attachment:filename=\"{0}\"",UrlFile ));
            if (context.Session["是否登录"] == null)
            {
                context.Response.Redirect("redirectLogin.htm");
 
            }
            else
            {
                int userId=(int)context .Session ["登录用户Id"];//从session中获得登录用户的id
                UsersTableAdapter adapter = new UsersTableAdapter();
                var data = adapter.GetDataById(userId );
                var user = data.Single();
                if (user.level == 0)//普通用户
                {
                    //给免费用户添加水印