判断用户是否登录

在项目中，往往会有一些操作是限于登录后的用户，但怎么判断用户是否登录呢？

首先，写一个类：需要验证登录的页面继承这个类就可以了

    public class CheckLogin:System.Web.UI.Page
    {
        protected override void OnInit(EventArgs e)
        {
            if (Session["user"]==null)
            {
                Common.WebCommon.GotoPage();//调用的方法是跳转页面的
            }
            base.OnInit(e);
        }
    }

登录页代码：

    public partial class Login : System.Web.UI.UserControl
    {
        BLL.Users userbll = new BLL.Users();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (IsPostBack)
            {
                //校验登陆密码用户名
                CheckLogin();
            }
            else
            {
                //校验cookie
                CheckCookie();
            }
        }
        /// <summary>
        /// 校验登陆
        /// </summary>
        private void CheckLogin()
        {
            string txtName = Request.Form["txtName"];
            string txtPass = Request["txtPass"];

            if (userbll.CheckLoginId(txtName))
            {
                Model.Users usermodel = userbll.CheckUserInfo(txtName, txtPass);
                Session["user"] = usermodel;
                if (usermodel != null)
                {
                    //判断用户是否选择了复选框
                    if (!string.IsNullOrEmpty(Request.Form["CheckMe"]))
                    {
                        HttpCookie cookie1 = new HttpCookie("cp1", txtName);
                        HttpCookie cookie2 = new HttpCookie("cp2", Entry(txtPass));
                        //cookie1.Expires.AddDays(3);
                        cookie1.Expires = DateTime.Now.AddDays(3);
                        cookie2.Expires = DateTime.Now.AddDays(3);
                        Response.Cookies.Add(cookie1);
                        Response.Cookies.Add(cookie2);
                    } GotoPage("登陆成功！");
                }
                else
                {
                    Response.Redirect("/ShowMsg.aspx?msg=" + Server.UrlEncode("密码错误") + "&txt=" + Server.UrlEncode("登陆页面") + "&url=/regex/ULogin.aspx");
                }

            }
            else
            {
                //用户名不存在
                Response.Redirect("/ShowMsg.aspx?msg=" + Server.UrlEncode("用户名不存在") + "&txt=" + Server.UrlEncode("登陆页面") + "&url=/regex/ULogin.aspx");
            }
        }
        /// <summary>
        /// 登陆后跳转
        /// </summary>
        /// <param name="p"></param>
        private void GotoPage(string msg)
        {
            if (!string.IsNullOrEmpty(Request.QueryString["returnUrl"]))
            {
                Response.Redirect(Request.QueryString["returnUrl"]);
            }
            else
            {
                Response.Redirect("/ShowMsg.aspx?msg=" + Server.UrlEncode(msg) + "&txt=" + Server.UrlEncode("首页") + "&url=/ListBook/ListBook.aspx");

            }
        }
        /// <summary>
        /// 校验cookie
        /// </summary>
        private void CheckCookie()
        {
            if (Request.Cookies["cp1"] != null && Request.Cookies["cp2"] != null)
            {

                string name = Request.Cookies["cp1"].Value.ToString();
                string pwd = Request.Cookies["cp2"].Value.ToString();
                Model.Users usermodel = userbll.CheckUserInfo(name);
                string EntypwdModel = Entry(usermodel.LoginPwd);
                //密码一致
                if (EntypwdModel == pwd)
                {
                    Session["user"] = usermodel;
                    GotoPage("登陆成功");
                }

            }
            else
            {
                Response.Cookies["cp1"].Expires = DateTime.Now.AddDays(-1);
                Response.Cookies["cp2"].Expires = DateTime.Now.AddDays(-1);
            }
        }

        public string Entry(string pwd)
        {
            return Web.HRMD5.GetMd5FromString(Web.HRMD5.GetMd5FromString(pwd));
        }

    }