CORS in .NET Core

Question

I am trying to enable CORS in .NET Core in this way:

    public IConfigurationRoot Configuration { get; }

    public void ConfigureServices(IServiceCollecti         


        

Answer 1

In ASPNET CORE 2.0, The following works for me

   public void ConfigureServices(IServiceCollection services)
    {

        services.Configure<MvcOptions>(options =>
        {
            options.Filters.Add(new CorsAuthorizationFilterFactory("AllowSpecificOrigin"));
        });
        services.AddCors(options =>
        {
            options.AddPolicy("AllowSpecificOrigin",
                builder => builder.WithOrigins("http://localhost:5000").AllowAnyHeader()
                .AllowAnyMethod());
        });

        services.AddMvc()
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {

        loggerFactory.AddConsole();
        loggerFactory.AddDebug(LogLevel.Information);

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        // Shows UseCors with named policy.
        app.UseCors("AllowSpecificOrigin");

        app.UseStaticFiles();
        app.UseAuthentication();


        app.UseMvcWithDefaultRoute();
    }
}

Answer 2

this is actually is a bug in dotnet core.

try to add cors policy right in the "Configure" method.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        app.UseRouting();
        app.UseCors(option =>
            option.AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                );
    }

Answer 3

I just fixed my problem with Cors in Core 3.1. I was following almost every example and documentation out there. Unfortunately nothing worked until I did .Build() for the builder inside the AddPolicy portion.

        services.AddCors(options => {
            options.AddPolicy(
                name: OrginPolicyKey, 
                builder => builder.WithOrigins("http://localhost:3000")
                    .AllowAnyHeader()
                    .AllowAnyMethod()
                    .Build() // <--- This right here
            );
        });

Also, other people were mentioning about calling the UseCors(OrginPolicyKey) before the rest of your routing and UseMvc stuff. That is correct and I saw that Putting UseCors after the route part broke it. Below is how mine is setup.

        app.UseCors(OrginPolicyKey); // <--- First

        // Then routing stuff..
        app.UseRouting();
        app.UseEndpoints(endpoints =>
        {
            endpoints
                .MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}"
                );
        });

Who knew a builder needs to be built ;D

Answer 4

You just need to add this in ConfigureService Method of StartUp Class

services.AddCors ();

and this in Configure Method of Startup Class and it will work fine then

app.UseCors (builder => builder
                 .AllowAnyOrigin ()
                 .AllowAnyHeader ()
                 .AllowAnyMethod ());

There is nothing more to add to enable CORS in .Net Core