/// <summary>

         /// 图形验证码

         /// </summary>

         [HttpGet]

         public IActionResult ValidateCode1()

         {

             string code = "";

             string yzm_id = "YZM_TOKEN_" + Guid.NewGuid().ToString();

             System.IO.MemoryStream ms = YZM1.Create(out code);//生成验证码图片流

             HttpContext.Response.Headers.Add("Access-Control-Expose-Headers", "YZM_TOKEN");

             HttpContext.Response.Headers.Add("YZM_TOKEN", yzm_id);//验证码token 放入headers头

             HttpContext.Response.Headers.Add("Access-Control-Allow-Origin", "*");//允许跨域

             CacheService.Add(yzm_id, code, DateTime.Now.AddMinutes() - DateTime.Now);//放入缓存有效期1分钟

             return File(ms.ToArray(), @"image/png");

         }

         <div id="codeNum">

           <img id="codeNum1" src="" alt="验证码">

           <input type="hidden" id="yzm_token">

         </div>

 //验证码

     function generatedCode() {

       axios.get('https://localhost:44357/api/YZM', { responseType: 'blob' }).then

         (

           function (response) {

             var blob = response.data;

             var img = document.getElementById("codeNum1");

             document.getElementById("yzm_token").value = response.headers.yzm_token;

             img.onload = function (e) {

               window.URL.revokeObjectURL(img.src);

             };

             img.src = window.URL.createObjectURL(blob);

           }

         );

     function generatedCode1(){

       var xmlhttp;

       xmlhttp = new XMLHttpRequest();

       xmlhttp.open("GET", "https://localhost:44357/api/YZM", true);

       xmlhttp.responseType = "blob";

       xmlhttp.onload = function () {

         if (this.status == 200) {

           var blob = this.response;

           var img = document.getElementById("codeNum1");

           document.getElementById("yzm_token").value = this.getResponseHeader("yzm_token");

           img.onload = function (e) {

             window.URL.revokeObjectURL(img.src);

           };

           img.src = window.URL.createObjectURL(blob);

         }

       }

       xmlhttp.send();

     }