Async validation lands in Minimal APIs with .NET 11 Preview 6
Preview 6 adds AsyncValidationAttribute and IAsyncValidatableObject so DataAnnotations rules can hit the database before your endpoint runs, without blocking a thread.
Tag: validation
6 posts
How to add an endpoint filter to a minimal API in ASP.NET Core 11
A complete, working guide to endpoint filters in an ASP.NET Core 11 minimal API: AddEndpointFilter with an inline delegate, IEndpointFilter classes with DI, GetArgument and the Arguments list, short-circuiting with Results.Problem, FIFO/FILO ordering across multiple filters, group-level filters on MapGroup, and AddEndpointFilterFactory for signature-aware filters.
Migrate a minimal API from manual validation checks to built-in validation in ASP.NET Core 11
A step-by-step migration guide for replacing hand-rolled if-checks in ASP.NET Core 11 minimal API handlers with the built-in source-generated DataAnnotations validator: what breaks, which manual rules do and do not port, and how to verify the 400 ProblemDetails contract stays identical.
How to customize minimal API validation error responses with IProblemDetailsService in ASP.NET Core 11
Call AddProblemDetails with a CustomizeProblemDetails callback to reshape the 400 that built-in minimal API validation returns in ASP.NET Core 11: add a traceId, rewrite the title, switch 400 to 422, or take full control with a custom IProblemDetailsWriter.
Minimal API validation vs FluentValidation in ASP.NET Core 11: which should you pick?
Use the built-in source-generated validation for synchronous, attribute-expressible rules in ASP.NET Core 11; reach for FluentValidation when you need async rules, complex cross-field logic, or validation kept out of your domain models.
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.