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Tag: aspnetcore

80 posts · Page 2 of 8

2026-08-11 errors aspnetcore dotnet

Fix: The type or namespace name 'OpenApiReference' could not be found

OpenApiReference was deleted in Microsoft.OpenApi 2.0. Changing the using to Microsoft.OpenApi is not enough: replace each usage with a typed reference such as OpenApiSchemaReference.

2026-08-09 csharp dotnet dotnet-11

How to serve OpenAPI documentation with Scalar instead of Swagger UI in ASP.NET Core 11

Replace UseSwaggerUI with MapScalarApiReference in ASP.NET Core 11: routing, multiple documents, pre-filled auth, production gating, offline assets, and the Scalar-only OpenAPI extensions that mark endpoints stable or hidden.

2026-08-07 comparison dotnet aspnetcore

WebApplicationFactory vs Testcontainers for ASP.NET Core integration tests

They are not alternatives. WebApplicationFactory boots your app, Testcontainers boots your dependencies. Measured on .NET SDK 10.0.201: a container fixture costs 1.7 s per class against 10 ms for SQLite, and a HasMaxLength(16) violation that Postgres rejects with 22001 is silently accepted by SQLite.

2026-08-06 errors blazor aspnetcore

Fix: Attempting to reconnect to the server after a Blazor Server circuit disconnects

The reconnect modal means the SignalR circuit dropped, not that your app crashed. Decide whether the retry ended in failed or rejected, then fix sticky sessions, the 3-minute retention window, the 32 KB message limit, or persist circuit state with [PersistentState].

2026-08-06 comparison dotnet dotnet-11

gRPC vs REST vs SignalR for service-to-service calls in .NET 11

For internal service-to-service calls in .NET 11, default to gRPC when you own both ends of the contract and the call is point-to-point. Use REST with JSON when anything you do not control has to call the service. SignalR is not an RPC transport between services: reach for it only when one producer has to fan a message out to many long-lived consumers.

2026-08-05 errors dotnet dotnet-11

Fix: HTTP Error 500.30 - ASP.NET Core app failed to start after deploying to IIS

500.30 means your app threw during startup inside w3wp.exe. The real exception is already in the Windows Application event log under IIS AspNetCore Module V2. Read that first, then rank the fix: missing shared framework, x86/x64 app pool mismatch, missing config, or app pool permissions.

2026-08-03 csharp dotnet dotnet-11

How to validate options at startup with IValidateOptions<T> in .NET 11

Implement IValidateOptions<T>, register it in DI, and chain ValidateOnStart so a bad appsettings.json kills the process instead of the first request that touches it. Covers the .NET 11 Validate<TValidator>() overload, async validation through IAsyncValidateOptions<T>, and the three places ValidateOnStart silently does nothing.

2026-08-02 csharp dotnet dotnet-11

How to configure Kestrel to serve HTTP/3 in ASP.NET Core 11

A complete guide to enabling HTTP/3 on Kestrel in ASP.NET Core 11: the HttpProtocols.Http1AndHttp2AndHttp3 endpoint config, MsQuic platform requirements on Windows, Linux, and macOS, why the first request is never HTTP/3, how to verify with HttpClient and middleware, QuicTransportOptions tuning, and the firewall and proxy gotchas that make it silently fall back.

2026-08-01 comparison csharp dotnet

IOptions<T> vs IOptionsSnapshot<T> vs IOptionsMonitor<T> in .NET 11

Default to IOptions<T>. Use IOptionsMonitor<T> when a singleton has to see config reloads, and IOptionsSnapshot<T> only when a scoped consumer wants a value that is stable for one request. The deciding axis is the lifetime of the consumer, not the shape of the settings.

2026-07-30 errors blazor dotnet

Fix: JavaScript interop calls cannot be issued at this time (Blazor prerendering)

Prerendering runs your component on the server with no browser attached, so IJSRuntime throws. Move the call into OnAfterRenderAsync, gate it on RendererInfo.IsInteractive, or disable prerendering.