Preserve the RequestUrlPrefix of tenants when running the ModularBackgroundService (#18623)

Author: gvkries

src/OrchardCore/OrchardCore.Abstractions/BackgroundTasks/HttpContextExtensions.cs

@@ -166,7 +166,7 @@ await shellScope.UsingAsync(async scope =>
                         try
                         {
                             // Use the base url, if defined, to override the 'Scheme', 'Host' and 'PathBase'.
-                            _httpContextAccessor.HttpContext.SetBaseUrl((await siteService.GetSiteSettingsAsync()).BaseUrl);
+                            SetBaseUrl(_httpContextAccessor.HttpContext, (await siteService.GetSiteSettingsAsync()).BaseUrl);
                         }
                         catch (Exception ex) when (!ex.IsFatal())
                         {
@@ -430,4 +430,27 @@ private void CleanSchedulers(string tenant, IEnumerable<IBackgroundTask> tasks)
             }
         }
     }
+
+    private static void SetBaseUrl(HttpContext context, string baseUrl)
+    {
+        if (!Uri.TryCreate(baseUrl, UriKind.Absolute, out var uri))
+        {
+            return;
+        }
+
+        context.Request.Scheme = uri.Scheme;
+        context.Request.Host = new HostString(uri.Host, uri.Port);
+
+        // Set the PathBase only if it's not just "/". Otherwise, the original path base is kept, which may
+        // contain the RequestUrlPrefix if any.
+        if (uri.AbsolutePath != "/")
+        {
+            context.Request.PathBase = uri.AbsolutePath;
+        }
+
+        if (!string.IsNullOrWhiteSpace(uri.Query))
+        {
+            context.Request.QueryString = new QueryString(uri.Query);
+        }
+    }
 }