Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SpaServices.ReactDevelopmentServer;
using Microsoft.AspNetCore.StaticFiles;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using OpenSpeechTools.Hubs;
using Newtonsoft;

namespace OpenSpeechTools
{
  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.AddControllersWithViews();

      // In production, the React files will be served from this directory
      services.AddSpaStaticFiles(configuration =>
      {
        configuration.RootPath = "ClientApp/build";
      });

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

      services.AddSignalR();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
      // Set up custom content types - associating file extension to MIME type
      var provider = new FileExtensionContentTypeProvider();
      // Add new mappings      
      provider.Mappings[".htm3"] = "text/html";
      provider.Mappings[".image"] = "image/png";
      provider.Mappings[".woff2"] = "application/font-woff2";
      provider.Mappings[".woff"] = "application/font-woff";

      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(new StaticFileOptions
      {
        ContentTypeProvider = provider
      });
      app.UseSpaStaticFiles();

      app.UseRouting();
      app.UseCors("CorsPolicy");
      app.UseEndpoints(endpoints =>
      {
        endpoints.MapControllerRoute(
                  name: "default",
                  pattern: "{controller}/{action=Index}/{id?}");
        endpoints.MapHub<DoctorPatient>("/doctor-patient");
        endpoints.MapHub<ModelData>("/model-data");
      });

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

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