CORS error keep happening even after enabling it, with .NET Core and Angular Client

问题

I have .net Core 3.0 Web API project where I have enabled the CORS as given:

ConfigureService

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

And in Configure method

app.UseCors();

And when ever I call this end point using httpclient from angular application I get CORS error.

And I can see the headers as in :

I thought adding the CORS in my startup should have solved this issue.

UPDATE:

Adding Configure and Configure Service Code:

public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();

        services.AddDbContext<LabSoftwareContext>(options => options.UseSqlServer(Configuration.GetConnectionString("LabDatabase")));

        services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", new OpenApiInfo
            {
                Version = "v1",
                Title = "Lab API",
                Description = "Lab Software APIs"
            });
        });

        services.Configure<IISServerOptions>(options =>
        {
            options.AutomaticAuthentication = false;
        });

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


public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseCors("AllowOrigin");

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

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

        app.UseSwagger();

        app.UseSwaggerUI(c =>
        {
            c.SwaggerEndpoint("/swagger/v1/swagger.json", "Lab Software API");
        });
    }

回答1:

I think the root cause of this is the order of your middleware in Configure() - if the order is incorrect it can cause unexpected Cors failures.

e.g. I think UseCors() might need to be placed after UseHttpsRedirection()

There is a (complex!) table explaining the ordering of middleware here: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/middleware/?view=aspnetcore-3.1#built-in-middleware

Your code modified according to the example from the same page:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
    }

    app.UseHttpsRedirection();

    app.UseRouting();
    app.UseCors();

    app.UseAuthentication();
    app.UseAuthorization();

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

    app.UseSwagger();

    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "Lab Software API");
    });
}

回答2:

[EnableCors("your_policy")]
public class BaseController : apiController

One thing that worked for me was to that despite putting on the Configure method was that i needed to specify the CORS in the controllers.

回答3:

write these at the end of Configure method

app.UseCors(x=>x.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader()); app.UseAuthentication();app.UseMvc();

also change https to http

来源：https://stackoverflow.com/questions/60091440/cors-error-keep-happening-even-after-enabling-it-with-net-core-and-angular-cli

标签

angular

asp.net-core

cors