CORS policy not work

[AuthorProxy]

server error: A CORS policy named 'CorsPolicy' could not be found.
client error:

xhr.js:178 OPTIONS http://05b9f069.ngrok.io/api/somemethod 500 (Internal Server Error)
btrips:1 Failed to load http://05b9f069.ngrok.io/api/somemethod: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. The response had HTTP status code 500.

ConfigureServices method:

void ConfigurePolicy(CorsPolicyBuilder builder)
{
    builder
        .WithOrigins("http://localhost", "http://localhost:3000")
        .AllowAnyOrigin()
        .AllowAnyMethod()
        .AllowAnyHeader()
        .AllowCredentials();
}

services.AddCors(options =>
{
    options.AddPolicy(StartupConstants.CorsPolicy, ConfigurePolicy);
});

services.AddMvc()

Configure method

app.UseCors(StartupConstants.CorsPolicy);
app.UseMvc();

[AuthorProxy]

Removing [EnableCors("AllowSpecificOrigin")] from controller fix 500 error and now no server errors, but 404 on client

Failed to load http://05b9f069.ngrok.io/api/btrips: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. The response had HTTP status code 404.

[blowdart]

The configure method you used doesn't create a named policy; you're mixing two approaches. The first approach applies CORS to the entire app, the second, the one with named policies only applies it to wherever you put the attribute.

Which approach are you wanting to use?

[AuthorProxy]

I want to set global cors based on tutorial https://docs.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-2.1
As i understand code below should enable global cors policy, and it's enough, isn't it?:

void ConfigurePolicy(CorsPolicyBuilder builder)
{
    builder
        .WithOrigins("http://localhost", "http://localhost:80", "http://localhost:8080", "http://localhost:3000", "http://localhost:3001")
        .AllowAnyOrigin()
        .AllowAnyMethod()
        .AllowAnyHeader()
        .AllowCredentials();
}

services.AddCors(options =>
{
    options.AddPolicy(StartupConstants.CorsPolicy, ConfigurePolicy);
});
...
app.UseCors(StartupConstants.CorsPolicy);