Cookie总是保存在客户端中，按在客户端中的存储位置，可分为内存Cookie和硬盘Cookie。
内存Cookie由浏览器维护，保存在内存中，浏览器关闭后就消失了，其存在时间是短暂的。硬盘Cookie保存在硬盘里，有一个过期时间，除非用户手工清理或到了过期时间，硬盘Cookie不会被删除，其存在时间是长期的。
Cookie的缺陷
- cookie会被附加在每个HTTP请求中，所以无形中增加了流量。
- 由于在HTTP请求中的cookie是明文传递的，所以安全性成问题。（除非用HTTPS）
- Cookie的大小限制在4KB左右。对于复杂的存储需求来说是不够用的。
ASP.NET C#读写Cookie
1 /// <summary> 2 /// 写cookie值 3 /// </summary> 4 /// <param name="strName">名称</param> 5 /// <param name="strValue">值</param> 6 public static void WriteCookie(string strName, string strValue) 7 { 8 HttpCookie cookie = HttpContext.Current.Request.Cookies[strName]; 9 if (cookie == null) 10 { 11 cookie = new HttpCookie(strName); 12 } 13 cookie.Value = UrlEncode(strValue); 14 HttpContext.Current.Response.AppendCookie(cookie); 15 } 16 17 /// <summary> 18 /// 写cookie值 19 /// </summary> 20 /// <param name="strName">名称</param> 21 /// <param name="strValue">值</param> 22 /// <param name="expires">过期时间(分钟)</param> 23 public static void WriteCookie(string strName, string strValue, int expires) 24 { 25 HttpCookie cookie = HttpContext.Current.Request.Cookies[strName]; 26 if (cookie == null) 27 { 28 cookie = new HttpCookie(strName); 29 } 30 cookie.Value = UrlEncode(strValue); 31 cookie.Expires = DateTime.Now.AddMinutes(expires); 32 HttpContext.Current.Response.AppendCookie(cookie); 33 } 34 35 /// <summary> 36 /// 写cookie值 37 /// </summary> 38 /// <param name="strName">名称</param> 39 /// <param name="key">键</param> 40 /// <param name="strValue">值</param> 41 public static void WriteCookie(string strName, string key, string strValue) 42 { 43 HttpCookie cookie = HttpContext.Current.Request.Cookies[strName]; 44 if (cookie == null) 45 { 46 cookie = new HttpCookie(strName); 47 } 48 cookie[key] = UrlEncode(strValue); 49 HttpContext.Current.Response.AppendCookie(cookie); 50 } 51 52 /// <summary> 53 /// 写cookie值 54 /// </summary> 55 /// <param name="strName">名称</param> 56 /// <param name="key">键</param> 57 /// <param name="strValue">值</param> 58 /// <param name="expires">过期时间(分钟)</param> 59 public static void WriteCookie(string strName, string key, string strValue, int expires) 60 { 61 HttpCookie cookie = HttpContext.Current.Request.Cookies[strName]; 62 if (cookie == null) 63 { 64 cookie = new HttpCookie(strName); 65 } 66 cookie[key] = UrlEncode(strValue); 67 cookie.Expires = DateTime.Now.AddMinutes(expires); 68 HttpContext.Current.Response.AppendCookie(cookie); 69 } 70 71 /// <summary> 72 /// 读cookie值 73 /// </summary> 74 /// <param name="strName">名称</param> 75 /// <returns>cookie值</returns> 76 public static string GetCookie(string strName) 77 { 78 if (HttpContext.Current.Request.Cookies != null && HttpContext.Current.Request.Cookies[strName] != null) 79 return UrlDecode(HttpContext.Current.Request.Cookies[strName].Value.ToString()); 80 81 return ""; 82 } 83 84 /// <summary> 85 /// 读cookie值 86 /// </summary> 87 /// <param name="strName">名称</param> 88 /// <returns>cookie值</returns> 89 public static string GetCookie(string strName, string key) 90 { 91 if (HttpContext.Current.Request.Cookies != null && HttpContext.Current.Request.Cookies[strName] != null && HttpContext.Current.Request.Cookies[strName][key] != null) 92 return UrlDecode(HttpContext.Current.Request.Cookies[strName][key].ToString()); 93 94 return ""; 95 }