使用CookieHelper帮助类：

public class CookieHelper    {        #region 获取Cookie        /// 
         /// 获得Cookie的值         /// 
         ///          /// 
              public static string GetCookieValue(string cookieName)        {            HttpRequest request = HttpContext.Current.Request;            if (request != null)                return GetCookieValue(request.Cookies[cookieName]);            return "";        }        /// 
         /// 获得Cookie的值         /// 
         ///          /// 
              public static string GetCookieValue(HttpCookie cookie)        {            if (cookie != null)            {                return cookie.Value;            }            return "";        }        /// 
         /// 获得Cookie         /// 
         ///          /// 
              public static HttpCookie GetCookie(string cookieName)        {            HttpRequest request = HttpContext.Current.Request;            if (request != null)                return request.Cookies[cookieName];            return null;        }        #endregion        #region 删除Cookie        /// 
         /// 删除Cookie        /// 
         ///          public static void RemoveCookie(string cookieName)        {            HttpResponse response = HttpContext.Current.Response;            if (response != null)            {                HttpCookie cookie = response.Cookies[cookieName];                if (cookie != null)                {                     response.Cookies.Remove(cookieName);                }            }        }        #endregion        #region 设置/修改Cookie                 /// 
         /// 设置Cookie         /// 
         ///          ///          ///          ///          public static void SetCookie(string cookieName,string value, DateTime? expires)        {            Guard.IsNotNullOrEmpty(cookieName, "cookieName");             HttpResponse response = HttpContext.Current.Response;            if (response != null)            {                HttpCookie cookie = response.Cookies[cookieName];                if (cookie != null)                {                    cookie.Value = value;                     if (expires != null)                        cookie.Expires = expires.Value;                    response.SetCookie(cookie);                }            }        }        #endregion        #region 添加Cookie                          /// 
         /// 添加为Cookie.Values集合         /// 
         ///          ///          ///          ///          public static void AddCookie(string cookieName,  string value, DateTime expires)        {            Guard.IsNotNullOrEmpty(cookieName, "cookieName");            HttpCookie cookie = new HttpCookie(cookieName);            cookie.Expires = expires;            cookie.Value = value;            AddCookie(cookie);        }        /// 
         /// 添加Cookie         /// 
         ///          public static void AddCookie(HttpCookie cookie)        {            HttpResponse response = HttpContext.Current.Response;            if (response != null)            {                //指定客户端脚本是否可以访问[默认为false]                 cookie.HttpOnly = true;                //指定统一的Path，比便能通存通取                 cookie.Path = "/";                //设置跨域,这样在其它二级域名下就都可以访问到了                 //cookie.Domain = "nas.com";                 response.AppendCookie(cookie);            }        }        #endregion    }

设置cookie：

public static string VCLoginName        {            get            {                try                {                    return CookieHelper.GetCookieValue("VCLoginName").ToStr();                }                catch                {                    return "0";                }            }            set            {                var cookie = CookieHelper.GetCookie("VCLoginName");                if (cookie != null)                {                    CookieHelper.SetCookie("VCLoginName", value, DateTime.Now.AddHours(1));                }                else                {                    //有效期，一个钟头                    CookieHelper.AddCookie("VCLoginName", value, DateTime.Now.AddHours(1));                }            }        }

设置：

SysContext.VCLoginName = user.LoginName;

js获取和设置cookie：

function getCookie(cname) {            console.log("开始")            console.log(document.cookie)            console.log("结束")            var arrStr = document.cookie.split("; ");                       for (var i = 0; i < arrStr.length; i++) {                var temp = arrStr[i].split("=");                if (temp[0] == cname) return unescape(temp[1]);            }        } //添加cookie        function addCookie(cname, cvalue, ctime) {            var str = cname + "=" + escape(cvalue);            if (ctime > 0) {                               //为时不设定过期时间，浏览器关闭时cookie自动消失                var date = new Date();                var ms = ctime * 3600 * 1000;                date.setTime(date.getTime() + ms);                str += "; expires=" + date.toGMTString();                alert(cname + cvalue);            }            document.cookie = str;        }

遇到的问题:

后台设置cookie但是通过js无法获取相应的cookie的值，why？

不知道。但是自己在一般处理程序中写的cookie却可以通过js获得。why？

HttpCookie cookie = new HttpCookie("LoginName", HttpUtility.UrlEncode(username)); //定义cookie对象以及名为DocUrl的项         DateTime dt = DateTime.Now;                  //定义时间对象         TimeSpan ts = new TimeSpan(0, 12, 20, 0);         //天，小时，分钟，秒  ,cookie有效作用时间        cookie.Expires = dt.Add(ts);                 //添加作用时间         context.Response.AppendCookie(cookie);               //确定写入cookie中

解决：

因为CookieHelper中设置了cookie的HttpOnly为true。

中HttpCookie对象的HttpOnly 属性 指定一个Cookie 是否可通过客户端脚本访问。不能通过客户端脚本访问为 true；否则为 false。默认值为 false。此属性并不能完全阻止客户端在本地获取cookies，但是可以增加通过脚本直接获取的难度。