问题 I'm working on a SignalR Core web app that uses the following stack: ASP.NET Core 2.1 preview 2 (2.1.0-preview2-final) SignalR Core 1.0 preview 2 (1.0.0-preview2-final) Microsoft.AspNetCore.Cors (2.1.0-preview2-final) Microsoft.AspNetCore.WebSockets (2.1.0-preview2-final) The client is using SignalR NPM package (@aspnet/signalr). The app is configured like so: public void ConfigureServices(IServiceCollection services) { services.AddCors(options => { options.AddPolicy( "CorsPolicy", builder =>