前后端分离项目，配置问题导致后端session丢失问题

今天遇到一个巨坑，后端写了获取验证码接口，以及验证验证码接口

获取验证码接口:

        /// <summary>
        /// 获取验证码
        /// </summary>
        /// <returns></returns>
        [AllowAnonymous]
        public FileResult VerificationCode()
        {
            return File(this.CreateCheckCodeImage(GenerateCheckCode()).ToArray(), "image/Gif");
        }

        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;

            System.Random random = new Random();

            for (int i = 0; i < 5; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else
                    code = (char)('A' + (char)(number % 26));
                if (code == '0')
                    code = 'M';
                checkCode += code.ToString();
            }

            Session["CheckCode"] = checkCode;

            return checkCode;
        }

        private MemoryStream CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return null;

            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 26.5)), 30);
            Graphics g = Graphics.FromImage(image);

            try
            {
                //生成随机生成器
                Random random = new Random();

                //清空图片背景色
                g.Clear(Color.White);

                //画图片的背景噪音线
                for (int i = 0; i < 25; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int y2 = random.Next(image.Height);

                    g.DrawLine(new Pen(Color.ForestGreen), x1, y1, x2, y2);
                }

                Font font = new System.Drawing.Font("Tahoma", 20, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.ForestGreen, Color.DarkRed, 1.2f, true);
                g.DrawString(checkCode, font, brush, -5, -5);

                //画图片的前景噪音点
                for (int i = 0; i < 80; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);

                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                return ms;
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

验证验证码接口:

        /// <summary>
        /// 验证 验证码是否正确
        /// </summary>
        /// <param name="Code"></param>
        /// <returns></returns>
        private bool CheckCode(string Code)
        {
            if (HttpContext.Current.Session["CheckCode"] == null)
            {
                HttpContext.Current.Session.Remove("CheckCode");
                return false;
            }
            if (HttpContext.Current.Session["CheckCode"].ToString().Equals(Code, StringComparison.CurrentCultureIgnoreCase) == false)
            {
                HttpContext.Current.Session.Remove("CheckCode");
                return false;
            }
            HttpContext.Current.Session.Remove("CheckCode");
            return true;
        }

使用的测试工具是APIpost，经过测试两个接口通过session存取验证码没有问题，都是可以调通的，但是部署项目的时候因为是前后端分离项目，需要配置跨域，跨域可以选择前端配置以及后端配置。

这里我使用的是后端配置

配置完成之后，前端调用验证码接口一直验证失败，经过日志输出，发现是session丢失问题，到这里有两个解决方案

方案一：更改配置信息，以及前端配置相关信息

跨域注意
1.前端ajax访问时要加上“xhrFields: {withCredentials: true}” ，实现session可以传递；
2.配置拦截器，response.setHeader(“Access-Control-Allow-Origin”, “*”)，实现跨域访问问题；
3.配置拦截器，response.addHeader(“Access-Control-Allow-Credentials”, “true”)，实现session传值问题；*
4.配置拦截器，如果配置了Access-Control-Allow-Credentials=true，则跨域拦截Access-Control-Allow-Origin 必须是指定的url，response.setHeader(“Access-Control-Allow-Origin”, url);

方案二：使用其他技术实现验证验证码，这里我使用的是缓存

CacheHelp.Set(
key: "验证码缓存",
value: checkCode,
Seconds: 7200 //缓存时长，单位“秒”
);

我这里给出一个缓存帮助类

    public class CacheHelp
    {

        /// <summary>
        /// 缓存指定对象，设置缓存
        /// </summary>
        /// <param name="key">缓存的key</param>
        /// <param name="value">缓存的值</param>
        /// <param name="Seconds">设置缓存时间；单位：秒</param>
        /// <returns></returns>
        public static bool Set(string key, object value, double Seconds)
        {
            return Set(key, value, null, DateTime.Now.AddSeconds(Seconds), Cache.NoSlidingExpiration,
            CacheItemPriority.Default, null);
        }

        /// <summary>
        /// 缓存指定对象，设置缓存
        /// </summary>
        public static bool Set(string key, object value, string path)
        {
            try
            {
                var cacheDependency = new CacheDependency(path);
                return Set(key, value, cacheDependency);
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 缓存指定对象，设置缓存
        /// </summary>
        public static bool Set(string key, object value, CacheDependency cacheDependency)
        {
            return Set(key, value, cacheDependency, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration,
            CacheItemPriority.Default, null);
        }

        /// <summary>
        /// 缓存指定对象，设置缓存
        /// </summary>
        public static bool Set(string key, object value, double seconds, bool isAbsulute)
        {
            return Set(key, value, null, (isAbsulute ? DateTime.Now.AddSeconds(seconds) : Cache.NoAbsoluteExpiration),
            (isAbsulute ? Cache.NoSlidingExpiration : TimeSpan.FromSeconds(seconds)), CacheItemPriority.Default,
            null);
        }

        /// <summary>
        /// 获取缓存对象
        /// </summary>
        public static object Get(string key)
        {
            return GetPrivate(key);
        }

        /// <summary>
        /// 判断缓存中是否含有缓存该键
        /// </summary>
        public static bool Exists(string key)
        {
            return (GetPrivate(key) != null);
        }

        /// <summary>
        /// 移除缓存对象
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static bool Remove(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                return false;
            }
            HttpRuntime.Cache.Remove(key);
            return true;
        }

        /// <summary>
        /// 移除所有缓存
        /// </summary>
        /// <returns></returns>
        public static bool RemoveAll()
        {
            IDictionaryEnumerator iDictionaryEnumerator = HttpRuntime.Cache.GetEnumerator();
            while (iDictionaryEnumerator.MoveNext())
            {
                HttpRuntime.Cache.Remove(Convert.ToString(iDictionaryEnumerator.Key));
            }
            return true;
        }

        /// <summary>
        /// 尝试获取缓存，不存在则执行匿名委托
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <param name="func"></param>
        /// <param name="Seconds">设置缓存时间；单位：秒</param>
        /// <returns></returns>
        public static T TryGet<T>(string key, Func<T> func, double Seconds)
        {
            if (Exists(key)) return (T)Get(key);
            var result = func.Invoke();
            Set(key, result, Seconds);
            return result;
        }

        /// <summary>
        /// 设置缓存
        /// </summary>
        public static bool Set(string key, object value, CacheDependency cacheDependency, DateTime dateTime,
        TimeSpan timeSpan, CacheItemPriority cacheItemPriority, CacheItemRemovedCallback cacheItemRemovedCallback)
        {
            if (string.IsNullOrEmpty(key) || value == null)
            {
                return false;
            }
            HttpRuntime.Cache.Insert(key, value, cacheDependency, dateTime, timeSpan, cacheItemPriority,
            cacheItemRemovedCallback);
            return true;
        }

        /// <summary>
        /// 获取缓存
        /// </summary>
        private static object GetPrivate(string key)
        {
            return string.IsNullOrEmpty(key) ? null : HttpRuntime.Cache.Get(key);
        }
    }

希望小伙伴们遇到这种问题时候能够有一个解决思路！！！！！