RegexRewriteWithCapture: a Microsoft.AspNetCore.Rewrite rule with regular expression and variable capture.

HomeController.cs

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
    }

    public IActionResult Index()
    {
        // use it in controller
        var valueFromRegexRewrite = Request.HttpContext.Items["RegexRewriteWithCapture"];
        return View(valueFromRegexRewrite);
    }

}

RegexRewriteWithCapture.cs

using Microsoft.AspNetCore.Rewrite;
using System.Text.RegularExpressions;


// the normal AddRedirect only rewrite the rule and loses the matches
// new RewriteOptions().AddRedirect("/test/(.*)","/handletest")
// if they're not in the redirect itself like
// new RewriteOptions().AddRedirect("/test/(.*)","/handletest/$1")
// RegexRewriteWithCapture captures the first match and redirects.
// it does not support matches in target url like $1, $2 ...

namespace RewriteRuleServerVariable.Configuration
{
    public class RegexRewriteWithCapture : IRule
    {
        private readonly Regex _rule;
        private readonly string _redirect;

        public RegexRewriteWithCapture(string regexRule, string redirect)
        {
            _rule = new Regex(regexRule, RegexOptions.Compiled);
            _redirect = redirect;
        }

        public void ApplyRule(RewriteContext context)
        {
            var request = context.HttpContext.Request;

            var match = _rule.Matches(request.Path.Value);

            if (match.Count > 0)
            {
                var response = context.HttpContext.Response;
                context.Result = RuleResult.SkipRemainingRules;
                context.HttpContext.Items.Add(nameof(RegexRewriteWithCapture), match[0].Value);
                context.HttpContext.Request.Path = _redirect;
            }
        }
    }
}

startup.cs

// add it to your Configure startup.cs
//.....
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/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();
            }
// USAGE:
            var options = new RewriteOptions()
            .Add(new RegexRewriteWithCapture("redirect/rule/(.*)", "/Home/Index"));
            app.UseRewriter(options);

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
        
 //.....