Conditional validation based on request route with asp.net core 2.2 and FluentValidation

Question

So Basically i wrote a validator for my class with FluentValidation and also a filter to do the validation task for me in my webAPI project, so far it's OK but assume that my User class has firstname,lastname,email,password properties and i have two routes (one for register and the other one for login) and as you might have noticed required properties are different on these route.

Thus,should I really need to write individual validation for each and every action i have?because this makes a lot of code code duplication and it's hard to change.is there any way to just add required condition based on the request coming with single validation class? Any suggestion???

Arian Dashti Arian Dashti · Accepted Answer · 2019-07-22T23:03:05

A better practice would be to use a factory pattern for your validations and use a an action filter to short circuit bad requests. You could validate any action argument(Headers, Request Bodies, etc..) with something like this.

public class TestValidationAttribute : Attribute, IActionFilter
{
    private string _requestModelName;

    public TestValidationAttribute(string requestModelName)
    {
        _requestModelName = requestModelName;
    }

    public void OnActionExecuting(ActionExecutingContext context)
    {
        // using Microsoft.Extensions.DependencyInjection;
        var services = context.HttpContext.RequestServices;
        var accessor = services.GetService<IHttpContextAccessor>();
        var factory = services.GetService<ITestValidatorFactory>();

        var tokens = accessor.HttpContext.GetRouteData().DataTokens;
        if (!tokens.TryGetValue("RouteName", out var routeNameObj))
        {
            throw new Exception($"Action doesn't have a named route.");
        }
        var routeName = routeNameObj.ToString();

        var validator = factory.Create(routeName);
        if (!context.ActionArguments.TryGetValue(_requestModelName, out var model))
        {
            throw new Exception($"Action doesn't have argument named {_requestModelName}.");
        }

        TestModel test;
        try
        {
            test = (TestModel) model;
        }
        catch (InvalidCastException)
        {
            throw new Exception($"Action argument can't be casted to {nameof(TestModel)}.");
        }

        var validation = validator.Validate(test);
        if (!validation.Successful)
        {
            context.Result = new BadRequestObjectResult(validation.ResponseModel);
        }
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
    }
}

public class TestController : Controller
{
    [HttpPost]
    [Route("Test/{id}", Name = "TestGet")]
    [TestValidation("model")]
    public IActionResult Test(TestModel model)
    {
        return Ok();
    }
}

public class ValidationResult
{
    public bool Successful { get; }
    public ResponseModel ResponseModel { get; }
}

public class TestModel
{
}

public interface ITestValidator
{
    ValidationResult Validate(TestModel model);
}

public interface ITestValidatorFactory
{
    ITestValidator Create(string routeName);
}

Conditional validation based on request route with asp.net core 2.2 and FluentValidation

1 Answers