基于 oauth2.0 协议，
具体原理可以参考：https://www.ruanyifeng.com/blog/2018/07/json_web_token-tutorial.html
public class JWTHelper{private const string salt = "123";//盐//获得jwt令牌public static string Create(string info){Dictionary<string, string> header = new Dictionary<string, string>();header.Add("alg", "MD5");header.Add("typ", "JWT");Dictionary<string, object> payload = new Dictionary<string, object>();//JWT 官方字段DateTime now = System.DateTime.Now;payload.Add("exp", now.AddHours(24));//过期时间payload.Add("nbf", now);//生效时间payload.Add("iat", now);//签发时间//jwt 特有字段payload.Add("info", info);string base64Header = Base64Url(Newtonsoft.Json.JsonConvert.SerializeObject(header));string base64Payload = Base64Url(Newtonsoft.Json.JsonConvert.SerializeObject(payload));string tmp = base64Header + "." + base64Payload;string sign = Md5(tmp + salt);//加盐return base64Header + "." + base64Payload + "." + sign;}//校验是否合法，是否过期public static bool Check(string token, out string info){info= "";try{string[] arr = token.Split('.');string base64Header = arr[0];string base64Payload = arr[1];string sign = arr[2];var signCheck = Md5(base64Header + "." + base64Payload + salt);if (signCheck != sign){return false;}var dic = Newtonsoft.Json.JsonConvert.DeserializeObject<Dictionary<string, object>>(Base64UrlDecode(base64Payload));if (Convert.ToDateTime(dic["exp"]) < System.DateTime.Now){//过期了return false;}info = dic["info"].ToString();return true;}catch (Exception err){return false;}}//获得base64编码private static string Base64Url(string input){//Base64 有三个字符+、/和=，在 URL 里面有特殊含义，所以要被替换掉：=被省略、+替换成-，/替换成_ 。string output = "";byte[] bytes = System.Text.Encoding.UTF8.GetBytes(input);try{output = Convert.ToBase64String(bytes).Replace('+', '-').Replace('/', '_').TrimEnd('=');}catch (Exception e){throw e;}return output;}//获得base64解码private static string Base64UrlDecode(string input){string output = "";input = input.Replace('-', '+').Replace('_', '/');switch (input.Length % 4){case 2:input += "==";break;case 3:input += "=";break;}byte[] bytes = Convert.FromBase64String(input);try{output = System.Text.Encoding.UTF8.GetString(bytes);}catch{output = input;}return output;}//获得md5校验码private static string Md5(string input, int bit = 16){System.Security.Cryptography.MD5CryptoServiceProvider md5Hasher = new System.Security.Cryptography.MD5CryptoServiceProvider();byte[] hashedDataBytes;hashedDataBytes = md5Hasher.ComputeHash(System.Text.Encoding.GetEncoding("gb2312").GetBytes(input));System.Text.StringBuilder tmp = new System.Text.StringBuilder();foreach (byte i in hashedDataBytes){tmp.Append(i.ToString("x2"));}if (bit == 16)return tmp.ToString().Substring(8, 16);elseif (bit == 32) return tmp.ToString();//默认情况else return string.Empty;}}