c#通用登录模块，简单好用，一贴见效

// 举个例子：一个网站有用户系统、商家系统、网站后台3个系统
//可以分3个userType, user ,shop , system
//网站后台一般都有角色，如admin,employee
//那么网站的角色就有 user,shop,admin,employee,但是admin和employee在一个客户端是不能同时登陆的，所以他们是同一类用户（system）

使用方法：

1、添加一个类LoginUser.cs 代码如下：

代码：

namespace MVCCommonAuth
{
    #region 功能说明
    // 举个例子：一个网站有用户系统、商家系统、网站后台3个系统
    //可以分3个userType, user ,shop , system
    //网站后台一般都有角色，如admin,employee
    //那么网站的角色就有 user,shop,admin,employee,但是admin和employee在一个客户端是不能同时登陆的，所以他们是同一类用户（system）
    #endregion

    public enum UserType
    {
        User,
        Shop,
        System
    }

    [Serializable]
    public class LoginUser
    {
        private static string DESKEY = DateTime.Now.ToString("1234MMdd");
        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>
        /// 从cookie读取用户信息
        /// </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登录
        /// </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 字符串加密

        /// <summary>   
        /// 利用DES加密算法加密字符串（可解密）   
        /// </summary>   
        /// <param name="plaintext">被加密的字符串</param>   
        /// <param name="key">密钥（只支持8个字节的密钥）</param>   
        /// <returns>加密后的字符串</returns>   
        private static string EncryptString(string plaintext, string key)
        {
            //访问数据加密标准(DES)算法的加密服务提供程序 (CSP) 版本的包装对象   
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);　//建立加密对象的密钥和偏移量   
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);　 //原文使用ASCIIEncoding.ASCII方法的GetBytes方法   

            byte[] inputByteArray = Encoding.Default.GetBytes(plaintext);//把字符串放到byte数组中   

            MemoryStream ms = new MemoryStream();//创建其支持存储区为内存的流　   
            //定义将数据流链接到加密转换的流   
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //上面已经完成了把加密后的结果放到内存中去   
            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }
        /// <summary>   
        /// 利用DES解密算法解密密文（可解密）   
        /// </summary>   
        /// <param name="ciphertext">被解密的字符串</param>   
        /// <param name="key">密钥（只支持8个字节的密钥，同前面的加密密钥相同）</param>   
        /// <returns>返回被解密的字符串</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);　//建立加密对象的密钥和偏移量，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对象，createDecrypt使用的是流对象，必须把解密后的文本变成流对象   
                StringBuilder ret = new StringBuilder();

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

        #endregion
    }
}

2、登录处理过程，写入cookie：

        [HttpPost]
        public ActionResult Login(string username,string userpass)
        {
            if (username=="admin" && userpass=="admin")
            {
                LoginUser loginuser = new LoginUser();
                loginuser.ID = 1;
                loginuser.UserName = username;
                loginuser.Roles = "Administrator";
                loginuser.Expires = DateTime.Now.AddHours(2);

                loginuser.Login("Administrator");

                return Content("登录成功");
                //return RedirectToAction("Index", "Home");
            }

            return RedirectToAction("Login");
        }

3、判断用户是否登录：

//是否登录
if(LoginUser.GetUserID("Administrator") > 0)
{

}


// 用户ID
int userID=LoginUser.GetUserID("Administrator")

//获取用户名
string userName= LoginUser.GetUser("Administrator").UserName