（MVC）验证用户是否登录

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace CommonHelper
{
    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true, AllowMultiple = true)]
    public class AuthorizationAttribute
    {
        private String _AuthUrl = String.Empty;

        /// <summary>
        /// 获取或者设置一个值，改值表示登录地址
        /// 如果web.config中未定义AuthUrl的值，则默认为login
        /// </summary>
        public String AuthUrl
        {
            get { return _AuthUrl; }
            set
            {
                if (String.IsNullOrEmpty(value))
                    throw new ArgumentNullException("用于验证用户登录信息的登录地址不能为空");
                else
                    _AuthUrl = value.Trim();
            }
        }

        private String _AuthSaveKey = String.Empty;
        /// <summary>
        /// 获取或者设置一个值，改值表示登录用来保存登录信息的键名
        /// 如果web.config中未定义AuthSaveKey的值，则默认为LoginedUser
        /// </summary>
        public String AuthSaveKey
        {
            get { return _AuthSaveKey; }
            set {
                if (String.IsNullOrEmpty(value))
                    throw new ArgumentNullException("用于保存登录信息的键名不能为空");
                else
                    this._AuthSaveKey = value.Trim();
            }
        }

        private String _AuthSaveType = String.Empty;
        /// <summary>
        /// 获取或者设置一个值，该值表示用来保存登录信息的方式
        /// </summary>
        public String AuthSaveType {
            get { return _AuthSaveType; }
            set {
                if (String.IsNullOrEmpty(value))
                    throw new ArgumentNullException("用于保存登录信息的方式不能为空，只能为【cookie】或者【session】");
                else
                    this._AuthSaveType = value.Trim();
            }
        }

        /// <summary>
        /// 默认构造函数
        /// </summary>
        public AuthorizationAttribute()
        { 
            String authUrl=System.Configuration.ConfigurationManager.AppSettings["AuthUrl"];
            String saveKey = System.Configuration.ConfigurationManager.AppSettings["AuthSaveKey"];
            String saceType = System.Configuration.ConfigurationManager.AppSettings["AuthSaveType"];

            if (String.IsNullOrEmpty(authUrl))
                this._AuthUrl = "/User/Login";
            else
                this._AuthUrl = authUrl;

            if (String.IsNullOrEmpty(saveKey))
                this._AuthSaveKey = "LoginedUser";
            else
                this._AuthSaveKey = saveKey;

            if (String.IsNullOrEmpty(saceType))
                this._AuthSaveType = "Session";
            else
                this._AuthSaveType = saceType;
        }

        /// <summary>
        /// 构造函数重载
        /// </summary>
        /// <param name="authUrl">表示没有登录跳转的登录地址</param>
        public AuthorizationAttribute(String authUrl)
            : this()
        {
            this._AuthUrl = authUrl;
        }

        /// <summary>
        /// 构造函数重载
        /// </summary>
        /// <param name="authUrl">表示没有登录跳转的登录地址</param>
        /// <param name="saveKey">表示登录用来保存登录信息的键名</param>
        public AuthorizationAttribute(String authUrl, String saveKey)
            : this(authUrl)
        {
            this._AuthSaveKey = saveKey;
            this._AuthSaveType = "Session";
        }

        /// <summary>
        /// 构造函数重载
        /// </summary>
        /// <param name="authUrl">表示没有登录跳转的登录地址</param>
        /// <param name="saveKey">表示登录用来保存登录信息的键名</param>
        /// <param name="saveType">表示登录用来保存登录信息的方式</param>
        public AuthorizationAttribute(String authUrl, String saveKey, String saveType)
            : this(authUrl, saveKey)
        {
            this._AuthSaveType = saveType;
        }

        /// <summary>
        /// 处理用户登录
        /// </summary>
        /// <param name="fileterContext"></param>
        public void OnAuthorization(AuthorizationContext fileterContext)
        {
            if (fileterContext.HttpContext == null)
                throw new Exception("次特性只适合于Web应用程序使用！");
            else {
                switch (AuthSaveType)
                { 
                    case "Session":
                        if (fileterContext.HttpContext.Session == null)
                            throw new Exception("服务器Session不可用！");
                        else if (!fileterContext.ActionDescriptor.IsDefined(typeof(AllowAnonymousAttribute), true) && !fileterContext.ActionDescription.ControllerDescriptor.IsDefined(typeof(AllowAnonymousAttribute), true))
                        {
                            if (fileterContext.HttpContext.Session[_AuthSaveKey] == null)
                                fileterContext.Result = new RedirectResult(_AuthUrl);
                        }
                        break;
                    case "Cookie":
                        if (!fileterContext.ActionDescriptor.IsDefined(typeof(AllowAnonymousAttribute), true) && !fileterContext.ActionDescriptor.ControllerDescriptor.IsDefined(typeof(AllowAnonymousAttribute), true))
                        {
                            if (fileterContext.HttpContext.Request.Cookies[_AuthSaveKey] == null)
                                fileterContext.Result = new RedirectResult(_AuthUrl);
                        }
                        break;
                    default:
                        throw new ArgumentNullException("用于保存登录信息的方式不能为空，只能为【Cookie】或者【Session】");
                }
            }
        }
    }
}