Sitecore ASP.NET Core Multisite

SitecoreOptions.cs

    public class SitecoreOptions
    {
        public static readonly string Key = "Sitecore";

        public Uri InstanceUri { get; set; }
        public string LayoutServicePath { get; set; } = "/sitecore/api/layout/render/jss";
        public string DefaultSiteName { get; set; }
        public string ApiKey { get; set; }
        public Uri RenderingHostUri { get; set; }
        public bool EnableExperienceEditor { get; set; }

        public Uri LayoutServiceUri
        {
            get
            {
                if (InstanceUri == null) return null;

                return new Uri(InstanceUri, LayoutServicePath);
            }
        }

        /**
         * ADDED TO THE GETTING STARTED EXAMPLE
         * This would be populated in your appsettings.json
         */
        public Dictionary<string, string> Sites { get; set; } = new Dictionary<string, string>();
    }

Startup.cs

public class Startup
{
    // snip - the rest of your Startup class

    public void ConfigureServices(IServiceCollection services)
    {
        // snip - routing, Mvc, Layout Service, etc
        
        // Register the Sitecore Rendering Engine services.
        services.AddSitecoreRenderingEngine(options =>
            {
                // snip - component registration


                /**
                 * HERE'S THE IMPORTANT BITS
                 * Dynamically set the site name passed to the layout service based on the incoming host name.
                 * Logic here is simple. You may want to support wildcards, ports, etc.
                 */
                options.MapToRequest((httpRequest, layoutRequest) =>
                {
                    var hostName = httpRequest.Host.Host;
                    var sites = Configuration.Sites;
                    
                    /** Set the site name dynamically based on host name **/
                    layoutRequest.SiteName(sites.ContainsKey(hostName) ? sites[hostName] : Configuration.DefaultSiteName);
                });
                
                
                
            })
            // snip - additional rendering engine config

        // snip - other services
    }

    // snip - the rest of your Startup class
}