ASP.NET Core 11 cheat sheet

ASP.NET Core's scope validation throws this when a singleton would capture a scoped dependency for the rest of the process. Make the consumer scoped, or take IServiceScopeFactory and create a scope on demand.

ASP.NET Core throws this when a constructor asks for a type that was never registered, was registered on the wrong container, or was added after the host was built. Three concrete fixes cover almost every case.

If GetConnectionString returns null in .NET 11, your appsettings.json is missing the key, not copied to the build output, or the wrong environment file is being selected. Three checks fix 95% of cases.

A complete guide to wiring Serilog 4.x and Seq 2025.2 into a .NET 11 ASP.NET Core app: AddSerilog vs UseSerilog, two-stage bootstrap logging, JSON configuration, enrichers, request logging, OpenTelemetry trace correlation, API keys, and the production gotchas around buffering, retention, and signal level.

Wire OpenTelemetry traces, metrics, and logs into a .NET 11 ASP.NET Core app with the OTLP exporter, then ship them to a free, self-hosted backend: the standalone Aspire Dashboard for local dev, Jaeger and SigNoz for self-hosted production, and the OpenTelemetry Collector when you need both.

A complete guide to per-endpoint rate limiting in ASP.NET Core 11: when to pick fixed window vs sliding window vs token bucket vs concurrency, how RequireRateLimiting and [EnableRateLimiting] differ, partitioning by user or IP, the OnRejected handler, and the distributed deployment pitfall everyone hits.

Stream Claude responses from an ASP.NET Core 11 minimal API end-to-end: the official Anthropic .NET SDK, TypedResults.ServerSentEvents, SseItem, IAsyncEnumerable, cancellation flow, and the gotchas that buffer your tokens silently. With Claude Sonnet 4.6 and Opus 4.7 examples.

Asp.Versioning 10.0 is the first release that targets .NET 10 and the new Microsoft.AspNetCore.OpenApi pipeline. Sander ten Brinke's April 23 walkthrough shows how to register one OpenAPI document per API version with WithDocumentPerVersion().

In .NET 11 the OpenAPI document is generated by Microsoft.AspNetCore.OpenApi and Swagger UI is no longer in the template. Here is how to wire Bearer, OAuth2 with PKCE, and OpenID Connect so the Authorize button actually works.

Two working paths in .NET 11: the built-in MapIdentityApi /refresh endpoint, and a custom JWT setup with refresh token rotation, family tracking, and reuse detection.

Upload multi-GB files to Azure Blob Storage from .NET 11 without loading them into memory. BlockBlobClient.UploadAsync with StorageTransferOptions, MultipartReader for ASP.NET Core uploads, and the buffering traps that put your payload on the LOH.

A complete .NET 11 walkthrough for shipping an ASP.NET Core minimal API with Native AOT: PublishAot, CreateSlimBuilder, source-generated JSON, the AddControllers limitation, IL2026 / IL3050 warnings, and EnableRequestDelegateGenerator for library projects.

A complete guide to global exception handling in ASP.NET Core 11: why IExceptionFilter is the wrong tool, how IExceptionHandler and UseExceptionHandler work together, ProblemDetails responses, multi-handler chains, and the .NET 10 diagnostics suppression breaking change.

Use Kiota, Microsoft's official OpenAPI code generator, to produce a fluent, strongly typed C# client from any OpenAPI spec. Step-by-step: install, generate, wire into ASP.NET Core DI, and handle authentication.

Serve large files from ASP.NET Core 11 without loading them into memory. Three tiers: PhysicalFileResult for on-disk files, Results.Stream for arbitrary streams, and Response.BodyWriter for generated payloads -- with code for each.

A HMAC validation flaw in Microsoft.AspNetCore.DataProtection 10.0.0 through 10.0.6 lets attackers forge ciphertexts. .NET 10.0.7 is the mandatory fix.

.NET 11 Preview 3 lets Kestrel serve HTTP/3 requests before the peer's control stream and SETTINGS frame arrive, shaving handshake latency off the first request on every new QUIC connection.

ASP.NET Core in .NET 11 Preview 3 teaches the Virtualize component to measure items at runtime, fixing the spacing and scroll jitter that uniform-height assumptions caused.

ASP.NET Core in .NET 11 Preview 2 brings TempData to Blazor static server-side rendering, enabling flash messages and Post-Redirect-Get flows without workarounds.

ASP.NET Core in .NET 11 Preview 2 adds OpenTelemetry semantic attributes directly to HTTP server activity, removing the need for OpenTelemetry.Instrumentation.AspNetCore.

Kestrel's HTTP/1.1 request parser in .NET 11 replaces BadHttpRequestException with a result struct, cutting malformed-request overhead by up to 40%.

A new project template in .NET 11 Preview 2 scaffolds the JS plumbing, WebWorkerClient, and JSExport boilerplate needed to run .NET code in a browser Web Worker.

If your Bearer token works in Postman but not in Scalar, the problem is likely your OpenAPI document. Here is how to declare a proper security scheme in .NET 10.

Fix the 'dotnet-ef does not exist' / 'dotnet ef command not found' error by installing the EF Core CLI as a global or local .NET tool.

Fix the 'Microsoft.NetCore.App or Microsoft.AspNetCore.App was not found' error by updating your Azure App Service stack and .NET runtime version.