lottery/website/Extensions/RewriteSubdomainRule.cs

using Microsoft.AspNetCore.Rewrite;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace NcGamesWebView.Extensions
{
    public class RewriteSubdomainRule : IRule
    {
        public void ApplyRule(RewriteContext context)
        {
            var request = context.HttpContext.Request;
            var host = request.Host.Host;
            // Check if the host is subdomain.domain.com or subdomain.localhost for debugging
            if (Regex.IsMatch(host, @"^[A-Za-z\d]+\.(?:[A-Za-z\d]+\.[A-Za-z\d]+|localhost)$"))
            {
                string subdomain = host.Split('.')[0];
                //modifying the request path to let the routing catch the subdomain
                context.HttpContext.Request.Path = "/subdomain/" + subdomain + context.HttpContext.Request.Path;
                context.Result = RuleResult.ContinueRules;
                return;
            }
            context.Result = RuleResult.ContinueRules;
            return;
        }
    }
}