For years, the biggest criticism of Minimal APIs in ASP.NET Core was the lack of native request validation. Developers either relied on third-party libraries like FluentValidation or wrote repetitive manual checks inside every endpoint handler. With .NET 10, that gap is officially closed.
How Built-In Validation Works
The new validation pipeline integrates directly into the Minimal API request lifecycle. During startup, you call builder.Services.AddValidation() to register a validation filter. This filter inspects your existing Data Annotation attributes automatically, including [Required], [MaxLength], [Range], and all other standard annotations.
If validation fails, the request never reaches your handler. The pipeline short-circuits and returns a 400 status code with a structured Problem Details response. There are no manual if-checks required and no try-catch wrappers needed.
Broader Scope Than Expected
What makes this particularly noteworthy is the scope of validation coverage. The new system validates query strings, headers, and route parameters, not just the request body. This is a broader reach than most developers anticipate, and it eliminates several categories of bugs that previously required custom middleware or filters.
Performance by Design
The implementation uses source-generated interceptors, which means you get compile-time safety without the reflection overhead that typically comes with runtime validation. This approach aligns with ASP.NET Core’s broader move toward ahead-of-time compilation and native AOT support.
Takeaway
If you have been holding off on adopting Minimal APIs for production services because of the validation story, that barrier no longer exists. The combination of native Data Annotation support, pipeline short-circuiting, and source-generated performance makes this a production-ready validation solution out of the box.
