fix: improve in-memory sitemap endpoint quality and correctness

Follow-up addressing issues from dual AI review (GPT-5.5 + Opus 4.6).

- Use [OutputCache(Duration=3600)] instead of [ResponseCache]; register AddOutputCache/UseOutputCache in Program.cs for real server-side caching
- Remove [FromServices] workaround; expose protected RouteConfigurationService in BaseController to avoid CS9107 double-capture
- Drop LastModificationDate on static controller routes (UtcNow as lastmod is an SEO anti-pattern)
- Filter sitemap route from route discovery so /sitemap.xml does not list itself
- Add [EnableRateLimiting] to SitemapXml action for consistency
- Accept IEnumerable<SiteMapping> to avoid unnecessary .ToList() allocation
- Fix startup log messages: generation -> validation

Author: BenjaminMichaelis

EssentialCSharp.Web/Controllers/BaseController.cs

@@ -16,6 +16,8 @@ protected BaseController(IRouteConfigurationService routeConfigurationService, I
         _HttpContextAccessor = httpContextAccessor;
     }
 
+    protected IRouteConfigurationService RouteConfigurationService => _RouteConfigurationService;
+
     public override void OnActionExecuting(ActionExecutingContext context)
     {
         // Automatically add static routes to all views

EssentialCSharp.Web/Controllers/HomeController.cs

@@ -5,6 +5,7 @@
 using EssentialCSharp.Web.Services;
 using HtmlAgilityPack;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.OutputCaching;
 using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.CodeAnalysis;
 using Microsoft.Extensions.Options;
@@ -90,10 +91,11 @@ public IActionResult Guidelines()
     }
 
     [Route("/sitemap.xml")]
-    [ResponseCache(Duration = 3600)]
-    public IActionResult SitemapXml([FromServices] IRouteConfigurationService sitemapRouteConfig)
+    [OutputCache(Duration = 3600)]
+    [EnableRateLimiting("content")]
+    public IActionResult SitemapXml()
     {
-        SitemapXmlHelpers.GenerateSitemapXml(siteMappingService.SiteMappings.ToList(), sitemapRouteConfig, siteSettings.Value.BaseUrl, out var nodes);
+        SitemapXmlHelpers.GenerateSitemapXml(siteMappingService.SiteMappings, RouteConfigurationService, siteSettings.Value.BaseUrl, out var nodes);
         return new SitemapProvider().CreateSitemap(new SitemapModel(nodes));
     }
 

EssentialCSharp.Web/Helpers/SitemapXmlHelpers.cs

@@ -18,7 +18,7 @@ public static void EnsureSitemapHealthy(List<SiteMapping> siteMappings)
         }
     }
 
-    public static void GenerateSitemapXml(List<SiteMapping> siteMappings, IRouteConfigurationService routeConfigurationService, string baseUrl, out List<SitemapNode> nodes)
+    public static void GenerateSitemapXml(IEnumerable<SiteMapping> siteMappings, IRouteConfigurationService routeConfigurationService, string baseUrl, out List<SitemapNode> nodes)
     {
         DateTime newDateTime = DateTime.UtcNow;
 
@@ -38,18 +38,17 @@ public static void GenerateSitemapXml(List<SiteMapping> siteMappings, IRouteConf
         // Add routes dynamically discovered from controllers
         var allRoutes = routeConfigurationService.GetStaticRoutes();
         var controllerRoutes = allRoutes
-            .Where(route => !route.Contains("error", StringComparison.OrdinalIgnoreCase)) // Skip Error actions for sitemap
-            .Where(route => !route.Contains("index", StringComparison.OrdinalIgnoreCase)) // Skip Index actions for sitemap
-            .Where(route => !route.Contains("identity", StringComparison.OrdinalIgnoreCase)) // Skip Identity actions for sitemap
-        // All routes should have leading slash
-            .Select(route => $"/{route}") // Add leading slash for sitemap URLs
+            .Where(route => !route.Contains("error", StringComparison.OrdinalIgnoreCase))
+            .Where(route => !route.Contains("index", StringComparison.OrdinalIgnoreCase))
+            .Where(route => !route.Contains("identity", StringComparison.OrdinalIgnoreCase))
+            .Where(route => !route.Contains("sitemap", StringComparison.OrdinalIgnoreCase))
+            .Select(route => $"/{route}")
             .ToList();
 
         foreach (var route in controllerRoutes)
         {
             nodes.Add(new($"{baseUrl}{route}")
             {
-                LastModificationDate = newDateTime,
                 ChangeFrequency = GetChangeFrequencyForRoute(route),
                 Priority = GetPriorityForRoute(route)
             });

EssentialCSharp.Web/Program.cs

@@ -243,6 +243,7 @@ private static void Main(string[] args)
 
         // Add services to the container.
         builder.Services.AddRazorPages();
+        builder.Services.AddOutputCache();
         builder.Services.AddCaptchaService(builder.Configuration.GetSection(CaptchaOptions.CaptchaSender));
         builder.Services.AddSingleton<ISiteMappingService, SiteMappingService>();
         builder.Services.AddSingleton<IRouteConfigurationService, RouteConfigurationService>();
@@ -505,6 +506,7 @@ await McpJsonRpcResponseWriter.WriteErrorAsync(
         app.UseStaticFiles();
 
         app.UseRouting();
+        app.UseOutputCache();
 
         app.UseWhen(
             context => context.Request.Path.StartsWithSegments("/mcp"),
@@ -596,10 +598,10 @@ private static bool IsMcpTransportRequest(HttpRequest request) =>
     [LoggerMessage(Level = LogLevel.Error, Message = "Unhandled exception on {Path}")]
     private static partial void LogUnhandledException(ILogger<Program> logger, Exception? exception, PathString path);
 
-    [LoggerMessage(Level = LogLevel.Information, Message = "Sitemap.xml generation completed successfully during application startup")]
+    [LoggerMessage(Level = LogLevel.Information, Message = "Sitemap validation completed successfully during application startup")]
     private static partial void LogSitemapGenerationSucceeded(ILogger<Program> logger);
 
-    [LoggerMessage(Level = LogLevel.Error, Message = "Failed to generate sitemap.xml during application startup")]
+    [LoggerMessage(Level = LogLevel.Error, Message = "Failed to validate sitemap during application startup")]
     private static partial void LogSitemapGenerationFailed(ILogger<Program> logger, Exception exception);
 
     [LoggerMessage(Level = LogLevel.Warning, Message = "Ignoring invalid TryDotNet origin in CSP: {Origin}")]