在前后端分离的项目里，我们请求接口的流程一般是：

1. 用户使用用户名密码登录
2. 信息正确，接口返回token
3. 请求需要登录验证的接口，将token放到header里一起请求接口

这里介绍一下，在webapi项目里，token是怎么生成的？

1. 项目的引用里，右键：管理NuGet程序包
2. 搜索JWT，安装即可，要注意项目的.NetFrameWork 要大于等于4.6
   
3. 代码如下：
   

   public class TokenInfo
   {
       public TokenInfo()
       {
           UserName = "jack.chen";
           Pwd = "jack123456";
       }
       public string UserName { get; set; }
       public string Pwd { get; set; }
   }
   
   public class TokenHelper
   {
       public static string SecretKey = "This is a private key for Server";//这个服务端加密秘钥 属于私钥
       private static JavaScriptSerializer myJson = new JavaScriptSerializer();
       public static string GenToken(TokenInfo M)
       {
           var payload = new Dictionary<string, dynamic>
               {
                   {"UserName", M.UserName},//用于存放当前登录人账户信息
                   {"UserPwd", M.Pwd}//用于存放当前登录人登录密码信息
               };
           IJwtAlgorithm algorithm = new HMACSHA256Algorithm();
           IJsonSerializer serializer = new JsonNetSerializer();
           IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
           IJwtEncoder encoder = new JwtEncoder(algorithm, serializer, urlEncoder);
           return encoder.Encode(payload, SecretKey);
       }
   
       public static TokenInfo DecodeToken(string token)
       {
           try
           {
               var json = GetTokenJson(token);
               TokenInfo info = myJson.Deserialize<TokenInfo>(json);
               return info;
           }
           catch (Exception)
           {
   
               throw;
           }
       }
   
       public static string GetTokenJson(string token)
       {
           try
           {
               IJsonSerializer serializer = new JsonNetSerializer();
               IDateTimeProvider provider = new UtcDateTimeProvider();
               IJwtValidator validator = new JwtValidator(serializer, provider);
               IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
               IJwtDecoder decoder = new JwtDecoder(serializer, validator, urlEncoder);
               var json = decoder.Decode(token, SecretKey, verify: true);
               return json;
           }
           catch (Exception)
           {
               throw;
           }
       }
   }

4. 使用cookie也是一样，用户登录之后，用特定的方法生成cookie，返回到浏览器，浏览器每次请求接口或者访问页面的时候，都会带上cookie信息，用于身份验证
   c#生成cookie的方法
   

   public class UserModel
   {
       public string UserName { get; set; }
       public string Pwd { get; set; }
   }
   
   public class CookieHelper
   {
       private static JavaScriptSerializer myJson = new JavaScriptSerializer();
   
       /// <summary>
       /// 设置登录信息cookie
       /// </summary>
       /// <param name="model"></param>
       public static void SetUserCookie(UserModel model)
       {
           FormsAuthentication.SetAuthCookie(model.UserName, false);
           string userStr = myJson.Serialize(model);
           //创建ticket
           FormsAuthenticationTicket ticket = 
               new FormsAuthenticationTicket(1, model.UserName, DateTime.Now, 
               DateTime.Now + FormsAuthentication.Timeout, false, userStr);
           //加密
           var cookieValue = FormsAuthentication.Encrypt(ticket);
           var cookie = new HttpCookie(FormsAuthentication.FormsCookieName, cookieValue)
           {
               HttpOnly = true,
               Secure = FormsAuthentication.RequireSSL,
               Domain = FormsAuthentication.CookieDomain,
               Path = FormsAuthentication.FormsCookiePath
           };
           //写入cookie
           HttpContext.Current.Response.Cookies.Remove(cookie.Name);
           HttpContext.Current.Response.Cookies.Add(cookie);
       }
   
       /// <summary>
       /// 获取登录信息的cookie
       /// </summary>
       /// <returns></returns>
       public static UserModel GetUserCookie()
       {
           var cookie = HttpContext.Current.Request.Cookies[FormsAuthentication.FormsCookieName];
           if (object.Equals(cookie, null) || string.IsNullOrEmpty(cookie.Value))
           {
               return null;
           }
           try
           {
               var ticket = FormsAuthentication.Decrypt(cookie.Value);
               if (!object.Equals(ticket, null) && !string.IsNullOrEmpty(ticket.UserData))
               {
                   UserModel userData = myJson.Deserialize<UserModel>(ticket.UserData);
                   return userData;
               }
           }
           catch (Exception)
           {
               
           }
           return null;
       }
   }