Dataannotations attribute
A DataAnnotations attribute is a .NET attribute that declares metadata or validation rules for types, members, and data-model elements.
ASP.NET Core in Action, 3e
DataAnnotations is the .NET attribute-based framework for declaring metadata and validation rules on types and their members.
- How it is used
- Declares expected user input on binding models for validation in minimal APIs, Razor Pages, and MVC.
- How deep it goes
- Works through property-level rules and framework validation behavior, including filter setup and a simple-parameter limitation.
- Examples
- Uses a user-details model with required names, email and phone formats, a display name, and an optional phone number.
- What you can do after
- Apply it via DataAnnotations attributes on binding models and arrange server-side handling appropriate to the ASP.NET Core framework.
Read how ASP.NET Core in Action, 3e explains dataannotations attribute →
Building Web APIs with ASP.NET Core
A data annotation is an attribute-based Entity Framework Core configuration mechanism that adds metadata to entity classes and their members.
- How it is used
- Uses attributes to configure EF Core entities and constrain input accepted by an ASP.NET Core API.
- How deep it goes
- Works through entity and endpoint attributes, then distinguishes configuration precedence and delegates composite-key configuration to Fluent API.
- Examples
- Shows BoardGame entity attributes and a [Range(1, 100)] page-size limit on GET /BoardGames.
- What you can do after
- Apply attributes to configure individual EF Core entity settings and reject out-of-range API inputs without manual checks.
Read how Building Web APIs with ASP.NET Core explains dataannotations attribute →
Related concepts
- validationconfigures · The process of checking data, behavior, systems, models, or results against defined criteria to assess their correctness, suitability, or acceptability.
- input tag helperused by · The Input Tag Helper is an ASP.NET Core Tag Helper that generates HTML input elements from a bound property and its metadata.
- FluentValidationalternative to · FluentValidation is a .NET validation library that defines object validation rules with a fluent programming interface.
- data-val-* attributeproduces · A data-val-* attribute is an HTML data attribute convention for encoding validation metadata used by unobtrusive client-side validation.
- attributekind of · A programming-language attribute is declarative metadata associated with a program element that provides information or directives to compilers, tools, frameworks, or runtimes.
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