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Model Binding & Validation

Model Binding Sources​

// From route
app.MapGet("/products/{id}", (int id) => { });

// From query string
app.MapGet("/products", (int page, int size) => { });

// From body
app.MapPost("/products", (Product product) => { });

// From header
app.MapGet("/", ([FromHeader(Name = "X-API-Key")] string apiKey) => { });

// From services
app.MapGet("/", (IProductService service) => { });

Data Annotations​

public class CreateProductRequest
{
    [Required(ErrorMessage = "Name is required")]
    [StringLength(100, MinimumLength = 3)]
    public string Name { get; set; }

    [Range(0.01, 10000)]
    public decimal Price { get; set; }

    [EmailAddress]
    public string ContactEmail { get; set; }
}

Automatic Validation​

[ApiController] // Enables automatic model validation
public class ProductsController : ControllerBase
{
    [HttpPost]
    public IActionResult Create(CreateProductRequest request)
    {
        if (!ModelState.IsValid)
            return BadRequest(ModelState);

        // Process valid model
    }
}

FluentValidation​

public class CreateProductValidator : AbstractValidator<CreateProductRequest>
{
    public CreateProductValidator()
    {
        RuleFor(x => x.Name)
            .NotEmpty()
            .Length(3, 100);

        RuleFor(x => x.Price)
            .GreaterThan(0)
            .LessThanOrEqualTo(10000);
    }
}

// Registration
builder.Services.AddFluentValidation(fv =>
    fv.RegisterValidatorsFromAssemblyContaining<CreateProductValidator>());

Resources​