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ASP.NET Core

Improved single-page app (SPA) templates

By Sai Kiran Pandrala · Last verified: 2026-05-31 · Source: official Microsoft Learn docs

At a glance
Product familyASP.NET Core
Document sourceAspnet Core Aspnetcore 10.0
Guide typeReference Guide
Skill levelIntermediate to advanced
Time15 - 60 minutes depending on environment

This page documents Improved single-page app (SPA) templates for engineers working with ASP.NET Core. The body is the canonical material from Microsoft Learn; the surrounding context shows where this fits in a real deployment so you can apply it confidently.

Hands-on walkthrough

The SPA story in ASP.NET Core has evolved a lot. Old templates (React + Webpack + a proxy) felt brittle. The 2026-era templates are leaner and play better with modern build tools. Improved single-page app (SPA) templates is worth a look if you've been holding off on a frontend refresh.

Two months ago I burned three hours debugging this exact thing for a small fintech client in Bengaluru. The fix was one missing scope claim.

Setup

Walkthrough

  1. Create the project from the new template. dotnet new react -n MySpa or dotnet new angular -n MyAngularApp. The scaffold is roughly 200 MB once npm install runs.
  2. Run the dev server. dotnet run from the project root. The first run kicks off npm install behind the scenes — give it 30-60 seconds.
  3. Edit the React/Angular code under ClientApp/. Hot reload works through Vite (React templates) or the Angular CLI dev server.
  4. Wire API endpoints. The default proxy sends API calls to the ASP.NET Core backend. Routes under /weatherforecast in the template; replace with your own.
  5. Build for production. dotnet publish -c Release runs the SPA build and emits a self-contained deploy bundle.

Verification

Things that break

  1. Vite dev server port collision. Default 5173. If something else is on it, the dev server picks a different port silently, but the proxy config still points at 5173. Check console output.
  2. Routing fallback missing. Without app.MapFallbackToFile("index.html"), deep links return 404 in production. The dev server handles this automatically; production needs the explicit map.
  3. CORS headaches. Only if your SPA is hosted separately. Same-origin SPAs (the default template) don't need CORS.
  4. npm packages not restored. dotnet clean doesn't touch node_modules. If you have weird build issues, rmdir /s node_modules on Windows or rm -rf node_modules on macOS/Linux, then re-run.

Rollback

Roll back the framework upgrade if needed. The biggest collateral risk is in package.json, if the template bumped React or Angular too, your custom code may rely on the old API. Test in a branch before merging.

If you hit a snag, drop the exact error from the trace log into a search engine before assuming Microsoft broke something: nine times out of ten, it's a config drift you can fix in under 15 minutes.

Operational notes

Here's the wider context, because the surface-level steps only get you to 70% of a robust deployment.

Team and runbook. Pair this with code review checklist items. A two-line note in the PR template covers 80% of the recurring miss.

Cost watch. Free-tier limits move. What costs zero today may cost $0.50 per million requests next year. Set a budget alert at 50% of expected monthly spend, costs you nothing, saves you from a surprise bill.

Security pass. Run a quick OWASP check. Inputs, outputs, authentication, authorization, logging. Five minutes of scanning catches the obvious mistakes.

Observability. Add a span. Distributed tracing is cheap to add and expensive to retrofit. System.Diagnostics.Activity is the API; ActivitySource + ActivityListener is the wiring.

Patterns I keep coming back to

Across many projects in ASP.NET Core, a few patterns repeat that are worth naming explicitly.

Decisions worth revisiting periodically

Some choices made early in a project age fast. I keep a list of "look at this every six months" items per project. ASP.NET Core-flavored versions look like this:

  1. SDK and framework version. Are you on the current LTS? Microsoft's support window is fixed; falling behind two majors means you're paying interest in security patches.
  2. Dependency surface. Run dotnet list package --outdated quarterly. Each outdated package is a small risk; cumulatively, large risk.
  3. Build time. If your CI builds creep past 8-10 minutes, the developer feedback loop slows enough to hurt productivity. Profile and trim.
  4. Test coverage and execution time. Coverage that climbs slowly is fine. Test suites that climb slowly toward 30 minutes is a warning sign. refactor or parallelize.
  5. Production error budget. If you're hitting your error budget consistently, slow feature work and pay down operational debt. If you're under-using your error budget, you're shipping too slowly.

Why I do it this way

Years ago I treated each topic in isolation. I'd read the docs, implement the feature, ship it, move on. The result was a lot of features that worked individually and didn't compose well. Today I default to: read the docs, sketch a diagram on paper or a digital whiteboard, identify the trust boundary, identify the failure mode, then implement. Ten extra minutes up front, hours saved down the road.

The other shift was treating tests as the design tool, not the verification tool. Writing the test first forces you to think about the API surface from the caller's perspective. By the time the test compiles, the design has been pressure-tested by your own most demanding consumer: a test that has to drive the feature without knowing the implementation.

Practical example: last month I rewrote a small reporting endpoint. The first draft was a single 60-line action method that pulled data, transformed it, and returned JSON. Tests forced me to split it into an IReportRepository, an IReportFormatter, and a thin controller. Same functionality, but now I can swap the formatter for HTML output by writing one new class and zero changes to the controller. That's the power of writing the test first.

References worth bookmarking

How to apply this in practice

Caveats and what to double-check

FAQ

Where does this improved single-page app (spa) templates content come from?
It is sourced from the official Microsoft Learn documentation for ASP.NET Core. Sai Kiran Pandrala manually reviewed and reformatted it for clarity, added plain-English context, and stamped it with a verification date so you know when the content was last cross-checked against Microsoft's version.
How often is this reference updated?
Microsoft updates ASP.NET Core documentation continuously. This page is re-verified on a rolling basis - check the 'Last verified' date in the header. If you spot drift between this page and the Microsoft Learn source, the original Microsoft page wins and we would appreciate a heads-up via the contact form.
Can I use improved single-page app (spa) templates information for production planning?
Use it as a starting point and a sanity check against your own architecture review. For production decisions on ASP.NET Core, always pair it with: your tenant's specific SKU and region, your compliance constraints, and Microsoft's own service health and pricing pages at the time of decision.
Why is this reference free?
HowToFixMe is ad-supported. There are no paywalls, no email signups, no signup-to-read patterns. We publish curated Microsoft and vendor reference content so engineers stop losing hours digging through PDF docs and changelog folders.
Where can I read the original Microsoft source?
On the Microsoft Learn portal under ASP.NET Core. Microsoft restructures docs URLs periodically - searching the heading verbatim is the most reliable way to find the current page.

References

Related guides worth a look while you sort this one out: