Auto API Validation with FluentValidation

Question

I want to auto apply validation for some models on requests execution. E.g. if I have a fluent validator for model A it will apply, if I don't have validator for model B then nothing happens. I wrote code, but maybe somebody can advise a better solution.

Answer 1

Create base class and interface:

public interface IBaseValidationModel
{
    public void Validate(object validator, IBaseValidationModel modelObj);
}

public abstract class BaseValidationModel<T> : IBaseValidationModel
{
    public void Validate(object validator, IBaseValidationModel modelObj)
    {
        var instance = (IValidator<T>)validator;
        var result = instance.Validate((T)modelObj);
    
        if (!result.IsValid && result.Errors.Any())
        {
            throw new Exception("INVALID");
        }
    }
}

Create model and validator:

public class LogInModel : BaseValidationModel<LogInModel>
{
    public string? Name { get; set; }
    public string? Password { get; set; }
    public string? Domain { get; set; }
}

public class LogInModelValidator : AbstractValidator<LogInModel>
{
    public LogInModelValidator()
    {
        RuleLevelCascadeMode = CascadeMode.Stop;

        RuleFor(x => x.Domain).NotNull().NotEmpty();
        RuleFor(x => x.Name).NotNull().NotEmpty();
        RuleFor(x => x.Password).NotNull().NotEmpty();
    }
}

Create action filter attribute to apply it to controllers:

public class ModelValidatorAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext context)
    {
        foreach (var actionArgument in context.ActionArguments)
        {
            //validate that model is having validator and resolve it
            if (actionArgument.Value is IBaseValidationModel model)
            {
                var modelType = actionArgument.Value.GetType();
                var genericType = typeof(IValidator<>).MakeGenericType(modelType);
                var validator = context.HttpContext.RequestServices.GetService(genericType);

                if (validator != null)
                {
                    // execute validator to validate model
                    model.Validate(validator, model);
                }
            }
        }
        
        base.OnActionExecuting(context);
    }
}

Controller:

[Route("account")]
[ModelValidator]
public class AccountController : ControllerBase
{
   public IActionResult Post([FromBody]LogInModel model)
   {
      return Ok("ok);
   }
}