title: Json method is not recognized in Web Api controller
body: <p>I have an web api controller </p>
  
  <pre><code>using sport.BLL.Abstract;
  using sport.BLL.Concrete;
  using sport.DAL.Entities;
  using sport.webApi.Models;
  using AutoMapper;
  using Microsoft.AspNet.Identity.EntityFramework;
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using Microsoft.AspNet.Identity;
  using Microsoft.AspNet.Identity.Owin;  
  using Microsoft.Owin.Security;
  using System.Net;
  using System.Net.Http;
  using System.Web.Http;
  using System.Web;
  using System.Web.WebPages.Html;
  
  namespace sport.webApi.Controllers 
  {
      public class AccountManageController : ApiController
      {
          [HttpPost]
          public System.Web.Mvc.ActionResult CreateAccount(CollaborateurModel item)
          {
              var user = new ApplicationUser { UserName = item.Username, Email = item.Email };
              var result = UserManager.CreateAsync(user, item.Password);
              if (result.Result.Succeeded)
              {
  
                  var currentUser = UserManager.FindByName(item.Username);
                  var roleresult = UserManager.AddToRole(currentUser.Id, item.Role);
                  ajt_collaborator entity = Mapper.Map&lt;CollaborateurModel, ajt_collaborator&gt;(item);
                  entity.id_user_fk = currentUser.Id;
                  entity.is_deleted = false; 
                  repo.CreateCollaborator(entity); 
                  var response = new { Success = true }; 
                  return  Json(response);
  
  
              }
              else
              {
                  var errorResponse = new { Success = false, ErrorMessage = "error" };
                  return  Json(errorResponse);
              }
  
          }
      }
  }
  </code></pre>
  
  <p>I got an error in this line :</p>
  
  <p><strong>return  Json(response);</strong></p>
  
  <p>the Json Method is not recognized!!! when I googled about that I get this <a href="https://msdn.microsoft.com/en-us/library/system.web.mvc.jsonresult%28v=vs.118%29.aspx">link</a> which indicates that <code>Json</code> method is included in <code>System.Web.Mvc</code>. Even I try to import this namespace I get the same error?</p>
  
  <ol>
  <li>So is the reason of this error?</li>
  <li>How can I fix it?</li>
  </ol>