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Tag: aspnetcore

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2026-08-27 dotnet csharp aspnetcore

How to render a heading whose level (h1-h6) is chosen at runtime in a Blazor component

Blazor has no syntax for a variable tag name, and DynamicComponent only renders component types. Override BuildRenderTree and call builder.OpenElement(0, $"h{level}"). Covers attribute splatting, why the tag name must be clamped before it reaches the DOM, why changing the level rips the element out of the DOM even with @key, and an auto-levelling variant built on a cascading value.

2026-08-20 aspnetcore dotnet error-handling

ASP.NET Core Stops Turning 413 Into 500 in UseExceptionHandler

A PR merged into dotnet/aspnetcore main on August 19, 2026 makes ExceptionHandlerMiddleware honour BadHttpRequestException.StatusCode instead of overwriting it with 500.

2026-08-20 errors dotnet dotnet-11

Fix: [FromForm] Dictionary<string, string> is always null in a minimal API

A [FromForm] Dictionary in a minimal API binds with an empty prefix: the form keys must be [key], not metadata[key]. Wrap it in a class to keep readable names.

2026-08-19 errors swashbuckle openapi

Fix: cannot target OpenAPI 3.0 after upgrading Swashbuckle.AspNetCore to v9

Swashbuckle 8 and later emit openapi 3.0.4, not 3.0.1, and there is no OpenApiSpecVersion for a patch version. Why it changed, and four ways to pin the string your tooling expects.

2026-08-19 errors openapi swagger

Fix: Swagger UI shows Unable to render this definition after upgrading to .NET 11

ASP.NET Core 11 emits openapi 3.2.0 by default and Swagger UI below 10.1.5 rejects it. Upgrade Swashbuckle.AspNetCore.SwaggerUI, or pin OpenApiVersion back to OpenApi3_1.

2026-08-16 csharp dotnet dotnet-11

How to download a file from a Blazor component without JavaScript interop

Skip the downloadFileFromStream JS module entirely. Render an anchor with the download attribute pointing at a minimal API endpoint that returns TypedResults.File, or POST a plain HTML form with an AntiforgeryToken. Covers why the download attribute is what stops Blazor's enhanced navigation from swallowing the click, why data-enhance silently discards the file, and the cookie-vs-bearer auth trap.

2026-08-15 comparison csharp dotnet

Scalar vs Swagger UI for OpenAPI documentation in ASP.NET Core 11

Scalar ships 1.02 MiB of gzipped JavaScript and a far better request builder. Swagger UI ships 514 KiB and renders OpenAPI 3.2, which is what .NET 11 now emits by default. Measured payloads, the 3.2 gap, endpoint routing on both sides, and the auth details that decide it.

2026-08-15 comparison dotnet dotnet-11

Zstandard vs Brotli vs Gzip response compression in .NET 11

Zstandard is the right default for dynamic API responses in .NET 11, but not at the quality the ASP.NET Core provider ships with. Benchmarks on real JSON payloads showing why quality 1 beats the default quality 3 on both size and CPU, when Brotli still wins, and why Gzip survives only as a fallback.

2026-08-13 dotnet-11 aspnetcore blazor

Blazor Server Circuits Now Pause Themselves When the Tab Goes Idle

.NET 11 Preview 7 adds an opt-in package that pauses interactive Server circuits when the browser tab is hidden, freeing memory and SignalR connections held by users who are not actually there.

2026-08-12 errors aspnetcore dotnet

Fix: The 'interceptors' feature is not enabled in this namespace

CS9137 comes from the Microsoft.AspNetCore.OpenApi source generator. Add InterceptorsNamespaces to every project that calls AddOpenApi, not just the one holding the PackageReference.