servicestack-validation

name	servicestack-validation
description	Applies FluentValidation and ServiceStack validation filters correctly.

ServiceStack Validation

ServiceStack uses FluentValidation to provide a declarative way to validate Request DTOs.

Defining Validators

• Create a class that inherits from AbstractValidator<TRequestDto>.
• Define rules in the constructor using the RuleFor syntax.
• Place validators in the ServiceInterface project (usually).

public class GetCustomerValidator : AbstractValidator<GetCustomer>
{
    public GetCustomerValidator()
    {
        RuleFor(r => r.Id).GreaterThan(0);
    }
}

Registration

Validators are automatically registered in the IoC container if you use the ValidationFeature.

// AppHost.Configure
Plugins.Add(new ValidationFeature());
container.RegisterValidators(typeof(MyServices).Assembly);

Validation Context

• Global Filters: The ValidationFeature installs a global request filter that automatically executes validators before the service.
• Error Responses: ServiceStack automatically converts validation failures into a ResponseStatus inside your Response DTO.

Manual Validation

While automatic validation is preferred, you can manually validate if needed:

var results = validator.Validate(request);
if (!results.IsValid)
    throw results.ToException();

Best Practices

• Validate Input ONLY: Use FluentValidation for validating the Request DTO structure, not complex business rules that require database state (though it's possible, keep it simple).
• Consistent Error Codes: Use .WithErrorCode() for custom error codes that clients can easily switch on.
• Client Metadata: Validation rules are exposed in the metadata, allowing clients (like TypeScript) to know the rules.