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Tag: aspnetcore-11

6 posts

2026-07-17 errors csharp dotnet

Fix: System.InvalidOperationException: Headers are read-only, response has already started

You set a header, status code, or content type after the body was already flushed. Set all headers before the first write, or guard with HttpResponse.HasStarted and OnStarting.

2026-06-16 migration swashbuckle openapi

Migrate from Swashbuckle to the built-in OpenAPI generator in .NET 11

A step-by-step migration from Swashbuckle.AspNetCore to Microsoft.AspNetCore.OpenApi in .NET 11: swapping AddSwaggerGen for AddOpenApi, converting operation, schema, and document filters to transformers, keeping a UI, and the Microsoft.OpenApi v2 breaking changes that bite.

2026-06-06 migration aspnetcore-11 dotnet-11

Migrate from IWebHostBuilder to WebApplication.CreateBuilder in .NET 11

A step-by-step migration from the old Startup.cs plus WebHostBuilder hosting model to the minimal hosting model with WebApplication.CreateBuilder, including the ASPDEPR008 deprecation, middleware ordering, IStartupFilter, and how to keep your tests working.

2026-06-06 migration aspnetcore-11 dotnet-11

Migrate from System.Web.HttpContext to Microsoft.AspNetCore.Http.HttpContext

A practical migration from the ASP.NET Framework System.Web.HttpContext to the ASP.NET Core 11 HttpContext: HttpContext.Current, the property map, Server.MapPath, Session, and the System.Web adapters shim for incremental migrations.

2026-05-12 errors csharp dotnet

Fix: InvalidOperationException: Synchronous operations are disallowed

Replace the Stream.Read or Write call with ReadAsync/WriteAsync. As a last resort, set AllowSynchronousIO on Kestrel, IIS, or per-request via IHttpBodyControlFeature.

2026-04-29 blazor blazor-webassembly aspnetcore-11

How to share validation logic between server and Blazor WebAssembly

The single biggest source of validation drift in a Blazor WebAssembly + ASP.NET Core app is the urge to write the rules twice. This guide walks the only layout that scales in .NET 11: a Shared class library that owns the DTOs and their validators, consumed by both the WASM client (EditForm + DataAnnotationsValidator or Blazored.FluentValidation) and the server (minimal API endpoint filter or MVC model binding), with a tested round-trip that maps server-side ValidationProblemDetails back into the EditContext.