title: ASP.NET 5/Core/vNext CORS not working even if allowing pretty much everything
body: <p>I have a ASP.NET 5 Web API (Well, MVC now anyway) back-end which I am consuming in with the <a href="https://github.com/mzabriskie/axios" rel="noreferrer">axios</a> library in my JS app.</p>
  
  <p>My CORS config in MVC is the following:</p>
  
  <pre><code>public void ConfigureServices(IServiceCollection services)
  {
        services.AddMvc();
        services.AddCors();
  } 
  
  
  public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
  { 
        app.UseCors(builder =&gt; {
            builder.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader();
        });
  }
  </code></pre>
  
  <p>So in other words, I should be allowing every request possible. However, while this fixed preflight requests, a POST requests still gets rejected (I can see it executes on the server, but there's no header in the response so it results in a client side error).</p>
  
  <p>Does anyone have any ideas why this wouldn't work ?</p>
  
  <p>These are the headers that are returned by the MVC api:</p>
  
  <ul>
  <li>For the OPTIONS preflight (this one passes):
  <a href="https://i.stack.imgur.com/MPk80.png" rel="noreferrer"><img src="https://i.stack.imgur.com/MPk80.png" alt="OPTIONS response"></a></li>
  <li>For the actual POST request (this one does NOT pass):
  <a href="https://i.stack.imgur.com/jxCLK.png" rel="noreferrer"><img src="https://i.stack.imgur.com/jxCLK.png" alt="POST response"></a></li>
  </ul>