.net core 3.1 c# cors not working with angular 7

Question

hi i have tried different ways to enable cors but failed my code is.am using spa app for presenting data but couldn't pass cors.browser shows the error Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:5000/Values. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).

 public void ConfigureServices(IServiceCollection services)
    {
       services.AddControllers().AddNewtonsoftJson(opt =>
        {
            opt.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
        });
        services.AddCors();
        services.AddSignalR();
        services.AddControllersWithViews();
        services.AddDbContext<DataContext>(x =>
        {
            x.UseLazyLoadingProxies();
            x.UseMySql(Configuration.GetConnectionString("DefaultConnection"));
        });
        IdentityBuilder builder = services.AddIdentityCore<User>(opt =>
        {opt.User.RequireUniqueEmail = true;            
        }).AddRoles<IdentityRole>();
        builder = new IdentityBuilder(builder.UserType, typeof(IdentityRole), builder.Services);
        builder.AddEntityFrameworkStores<DataContext>();
        builder.AddSignInManager<SignInManager<User>>();
        services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
            .AddJwtBearer(options =>
            {
                options.TokenValidationParameters = new TokenValidationParameters
                {
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII
                        .GetBytes(Configuration.GetSection("AppSettings:Token").Value)),
                    ValidateIssuer = false,
                    ValidateAudience = false

                };
                options.Events = new JwtBearerEvents
                {
                    OnMessageReceived = context =>
                    {
                        var accessToken = context.Request.Query["access_token"];
                        if (string.IsNullOrEmpty(accessToken) == false)
                        {
                            context.Token = accessToken;
                        }
                        return Task.CompletedTask;
                    }
                };
            });
        services.AddAuthorization(options =>
        {
            options.AddPolicy(constant.RequireVisionTrackAdminRole, policy => policy.RequireRole(constant.VisionTrackAdmin));
            options.AddPolicy(constant.RequireAdminRole, policy => policy.RequireRole(constant.Admin, constant.VisionTrackAdmin));
        });
        services.AddScoped<IAuthRepository, AuthRepository>();
        services.AddAutoMapper(typeof(VisionTrackRepository).Assembly);
        services.AddSpaStaticFiles(configuration =>
        {
            configuration.RootPath = "ClientApp/build";
        });
    }

 public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Error");
            // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
            app.UseHsts();
        }       
        app.UseHttpsRedirection();
        app.UseStaticFiles();
        app.UseSpaStaticFiles();          
        app.UseRouting();
        app.UseCors(
            options => options.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader()
        );
        app.UseAuthentication();
        app.UseAuthorization();
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapHub<VisionTrackHub>("/VisionTrack").RequireCors("CorsPolicy");
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller}/{action=Index}/{id?}").RequireCors("CorsPolicy");

        });
        app.UseSpa(spa =>
        {
            spa.Options.SourcePath = "ClientApp";

            if (env.IsDevelopment())
            {
                spa.UseReactDevelopmentServer(npmScript: "start");
            }
        });

    }

also tried this guide not working [https://learn.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-3.1] Is it because of authorization middle ware or is something to be done on endpoints?

mcjmzn · Accepted Answer · 2020-01-18 10:42:51Z

3

I think that's related to fact, that you cannot use both options.AllowAnyOrigin() and authentication middleware. In your case you are obliged to explicitly define allowed origins.

If you defined your CORS in a way given below, the request block should not happen.

services.AddCors(o => o.AddPolicy("CorsPolicy", builder =>
{
    builder
        .WithOrigins(new[]{"http://YOUR_FRONTEND_ORIGIN"})
        .AllowAnyMethod()
        .AllowAnyHeader()
        .AllowCredentials();
}));

app.UseCors("CorsPolicy");

answered Jan 18, 2020 at 10:42

mcjmzn

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1 Comment

JP Damstra Over a year ago

What for local? I.e. I'd use "example.com" as the origin paired with AllowCredentials, but how do I also AllowAnyOrigin for when I'm running on my dev machine?

hsn-mnj · Accepted Answer · 2020-09-20 04:41:44Z

2

In your Startup file you have two main method, ConfigureServices, and Configure method.

In you ConfigureServices method define it as below:

 services.AddCors(options =>
        {
            options.AddPolicy("CorsPolicy",
                builder => builder.AllowAnyOrigin()
                                  .AllowAnyMethod()
                                  .AllowAnyHeader());
        });

And in Configure method add this line:

app.UseCors("CorsPolicy");

Note: app.UseCors("CorsPolicy") should be after app.UseRouting() and before app.UserAuthentication()

answered Sep 20, 2020 at 4:41

hsn-mnj

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Comments

ABNER JACINTO · Accepted Answer · 2020-09-20 04:25:21Z

1

I resolved comment line //app.UseHttpsRedirection();

        //app.UseHttpsRedirection();           

        app.UseRouting();


        // global cors policy
        app.UseCors();


        app.UseAuthorization();

answered Sep 20, 2020 at 4:25

ABNER JACINTO

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Comments

HelloWorld1 · Accepted Answer · 2020-09-25 17:11:32Z

This solution solved my case:

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddCors();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseCors(
            options => options.SetIsOriginAllowed(x => _ = true).AllowAnyMethod().AllowAnyHeader().AllowCredentials()
        );

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

https://github.com/dotnet/aspnetcore/issues/16672

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