用法：

還是希望讀者把原始碼看懂，即可運用自如。重點是，為什麼有個UserType!!!

登入使用者資訊：

namespace MVCCommonAuth
{
    [Serializable]
    public class LoginUser
    {
        private const string DESKEY = "12345678";
        public int ID { get; set; }

        public string UserName { get; set; }
        
 
public string Roles { get; set; }

        public DateTime Expires { get; set; }

        public readonly static string CookieNamePrefix = "authcookie";

        public void Login(string userType, string domain = null, string path = null)
        {
            var keyName = CookieNamePrefix + userType;
            
 
var json = JsonConvert.SerializeObject(this);
            var value = EncryptString(json, DESKEY);

            HttpCookie cookie = new HttpCookie(keyName, value);
            cookie.Expires = Expires;
            if (!string.IsNullOrWhiteSpace(domain))
            {
                cookie.Domain 
 
= domain;
            }
            if (path != null)
            {
                cookie.Path = path;
            }
            HttpContext.Current.Items[keyName] = this;
            HttpContext.Current.Response.Cookies.Add(cookie);
        }


        /// <summary>
        /// 從cookie讀取使用者資訊
        /// </summary>
        /// <param name="cookieName"></param>
        private static LoginUser BuildUser(string keyName)
        {
            var cookie = HttpContext.Current.Request.Cookies[keyName];
            if (cookie != null && !string.IsNullOrEmpty(cookie.Value))
            {
                try
                {
                    var json = DecryptString(cookie.Value, DESKEY);
                    var loginuser = JsonConvert.DeserializeObject<LoginUser>(json);
                    if (loginuser != null)
                    {
                        if (loginuser.Expires >= DateTime.Now)
                        {
                            return loginuser;
                        }
                    }
                }
                catch
                {
                    //do nothing
                }
            }
            return null;
        }

        public static LoginUser GetUser(string userType)
        {
            var keyName = CookieNamePrefix + userType;
            if (!HttpContext.Current.Items.Contains(keyName))
            {
                var user = BuildUser(keyName);
                HttpContext.Current.Items[keyName] = user;
                return user;
            }
            else
            {
                return HttpContext.Current.Items[keyName] as LoginUser;
            }
        }

        public static int GetUserID(string userType)
        {
            var user = GetUser(userType);
            if (user != null)
                return user.ID;
            return 0;
        }

        /// <summary>
        /// 退出cookie登入
        /// </summary>
        public static void Logout(string userType)
        {
            var keyName = CookieNamePrefix + userType;

            HttpCookie cookie = new HttpCookie(keyName, string.Empty);
            cookie.Expires = DateTime.Now.AddMonths(-1);
            HttpContext.Current.Response.Cookies.Add(cookie);
        }


        #region 字串加密

        /// <summary>   
        /// 利用DES加密演算法加密字串（可解密）   
        /// </summary>   
        /// <param name="plaintext">被加密的字串</param>   
        /// <param name="key">金鑰（只支援8個位元組的金鑰）</param>   
        /// <returns>加密後的字串</returns>   
        private static string EncryptString(string plaintext, string key)
        {
            //訪問資料加密標準(DES)演算法的加密服務提供程式 (CSP) 版本的包裝物件   
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);　//建立加密物件的金鑰和偏移量   
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);　 //原文使用ASCIIEncoding.ASCII方法的GetBytes方法   

            byte[] inputByteArray = Encoding.Default.GetBytes(plaintext);//把字串放到byte陣列中   

            MemoryStream ms = new MemoryStream();//建立其支援儲存區為記憶體的流　   
            //定義將資料流連結到加密轉換的流   
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //上面已經完成了把加密後的結果放到記憶體中去   
            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }
        /// <summary>   
        /// 利用DES解密演算法解密密文（可解密）   
        /// </summary>   
        /// <param name="ciphertext">被解密的字串</param>   
        /// <param name="key">金鑰（只支援8個位元組的金鑰，同前面的加密金鑰相同）</param>   
        /// <returns>返回被解密的字串</returns>   
        private static string DecryptString(string ciphertext, string key)
        {
            try
            {
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();

                byte[] inputByteArray = new byte[ciphertext.Length / 2];
                for (int x = 0; x < ciphertext.Length / 2; x++)
                {
                    int i = (Convert.ToInt32(ciphertext.Substring(x * 2, 2), 16));
                    inputByteArray[x] = (byte)i;
                }

                des.Key = ASCIIEncoding.ASCII.GetBytes(key);　//建立加密物件的金鑰和偏移量，此值重要，不能修改   
                des.IV = ASCIIEncoding.ASCII.GetBytes(key);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);

                cs.Write(inputByteArray, 0, inputByteArray.Length);

                cs.FlushFinalBlock();

                //建立StringBuild物件，createDecrypt使用的是流物件，必須把解密後的文字變成流物件   
                StringBuilder ret = new StringBuilder();

                return System.Text.Encoding.Default.GetString(ms.ToArray());
            }
            catch (Exception)
            {
                return "error";
            }
        }

        #endregion
    }

}

Action驗證過濾器：

namespace MVCCommonAuth
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = false)]
    public class AuthFilterAttribute : ActionFilterAttribute
    {
        public AuthFilterAttribute() { }
        public AuthFilterAttribute(string roles,string userType) {
            this.Roles = roles;
            this.UserType = userType;
        }
        public bool Allowanonymous { get; set; }
        public string Roles { get; set; }

        public string Users { get; set; }

        public string UserType { get; set; }

        public sealed override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            if (Allowanonymous) return;
            if (IsAuth()) return;
            UnauthorizedRequest(filterContext);
        }

        public sealed override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);
        }
        public sealed override void OnResultExecuting(ResultExecutingContext filterContext)
        {
            base.OnResultExecuting(filterContext);
        }
        public sealed override void OnResultExecuted(ResultExecutedContext filterContext)
        {
            base.OnResultExecuted(filterContext);
        }

        private bool IsAuth()
        {
            var user = LoginUser.GetUser(UserType);
            if (user != null)
            {
                return AuthorizeCore(user.UserName, user.Roles);
            }
            else
            {
                return false;
            }
        }

        private void UnauthorizedRequest(ActionExecutingContext filterContext)
        {
            if (filterContext.HttpContext.Request.IsAjaxRequest())
                UnauthorizedAjaxRequest(filterContext);
            else
                UnauthorizedGenericRequest(filterContext);
        }

        protected virtual bool AuthorizeCore(string userName, string userRoles)
        {
            var separator = new char[] { ',' };
            var options = StringSplitOptions.RemoveEmptyEntries;
            if (!string.IsNullOrWhiteSpace(Users))
            {
                return Users.Split(separator, options).Contains(userName);
            }
            if (!string.IsNullOrWhiteSpace(Roles))
            {
                var allowRoles = Roles.Split(separator, options);
                var hasRoles = userRoles.Split(separator, options);
                foreach (var role in hasRoles)
                {
                    if (allowRoles.Contains(role))
                    {
                        return true;
                    }
                }
                return false;
            }
            return true;
        }

        protected virtual void UnauthorizedGenericRequest(ActionExecutingContext filterContext)
        {
            //根據Roles、Users、UserType資訊分別跳轉
            filterContext.Result = new RedirectResult("/Account/login?returnurl=" + filterContext.HttpContext.Request.Url.PathAndQuery);
        }
        protected virtual void UnauthorizedAjaxRequest(ActionExecutingContext filterContext)
        {
            var acceptTypes = filterContext.HttpContext.Request.AcceptTypes;
            if (acceptTypes.Contains("*/*") || acceptTypes.Contains("application/json"))
            {
                filterContext.Result = new JsonResult { Data = new { code = 0, msg = "nologin" }, JsonRequestBehavior = JsonRequestBehavior.AllowGet };
            }
            else
            {
                filterContext.Result = new ContentResult { Content = "nologin" };
            }

        }

    }
}