升级到.NET Core 2.2后的CORS问题

Question

I had an .NET Core 2.1 application which handled CORS well. But after upgrading to 2.2 I faced the problem:

Access to XMLHttpRequest at ' https://content.xxxx/user/avatar ' from origin ' https://cabinet.xxxx ' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Response Headers: (might this be an issue with IIS?)

Connection: close

Content-Length: 315

Content-Type: text/html; charset=us-ascii

Date: Tue, 22 Jan 2019 15:08:26 GMT

Server: Microsoft-HTTPAPI/2.0

I tried every combination I could find here (enabling CORS before and after MVC, adding and removing UseCors from Configure method), but nothing worked.

 public IServiceProvider ConfigureServices(IServiceCollection services)
    {
       ...
        services.AddCors(options =>
        {
            options.AddPolicy("MyPolicy",
                builder => builder.WithOrigins("https://cabinet.xxxxxx")
                                  .AllowAnyMethod()
                                  .AllowCredentials()
                                  .AllowAnyHeader());
        });


        services.AddMvc();
        ...
    }

   public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        app.UseHsts();
        //app.UseHttpsRedirection();
        app.UseCors("MyPolicy");
        app.UseMvc();
        app.UseDefaultFiles();
        app.UseStaticFiles();
    }

and the method is

    [HttpPost]
    [EnableCors("MyPolicy")]
    [Route("user/avatar")]
    [Authorize]
    public async Task Method(IFormFile file) {...}

Am I missing something? I don't want to downgrade back to 2.1.

Answer 1

Apparently there was an issue with IIS configuration. Moving website to another port helped.