CORS in .NET Core 2.0 "No 'Access-Control-Allow-Origin' header is present on the requested resource."

Question

I have created a web api using Core 2.0 and when doing cross domain calls w/ cors enabled, receive the following error: "No 'Access-Control-Allow-Origin' header is present on the requested resource."

Below is my config in startup.cs:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddLogging();
        services.AddMvc();
        services.AddCors(options =>
        {
            options.AddPolicy("AllowAll",
                builder =>
                {
                    builder
                    .AllowAnyOrigin()
                    .AllowAnyMethod()
                    .AllowAnyHeader();
                });
        });

        services.Configure<MvcOptions>(options =>
        {
            options.Filters.Add(new CorsAuthorizationFilterFactory("AllowAll"));
        });
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        loggerFactory.AddConsole(Configuration.GetSection("Logging"));
        loggerFactory.AddDebug();
        app.UseMvc();
        app.UseCors("AllowAll");    
    }

According to every post/tutorial I see on stackoverflow or else where, this is the correct way to do it to allow all origins. What am I missing?

Answer 1

Try calling: app.UseCors("AllowAll"); before app.UseMvc();.

The documentation states the following:

To enable CORS for your entire application add the CORS middleware to your request pipeline using the UseCors extension method. Note that the CORS middleware must precede any defined endpoints in your app that you want to support cross-origin requests (ex. before any call to UseMvc).