Route Parameter Validation with Date Format

Question

I am getting the validation failure message (status code 400) for all inputs, when i change the date format to string, the regex works but DateType validation not working. It accepts 2019-02-31 as a valid input. Any idea how to make it work DateTime parameter type?

    [HttpGet("{date}")]
    public ActionResult<string> Get( [RegularExpression(@"^[0-9]{4}-[0-9]{2}-[0-9]{2}$"), DataType(DataType.Date)] DateTime date)
    {
         return Ok();
    }

Answer 1

For Route Validation, you should avoid be used for input validation .

Don't use constraints for input validation. If constraints are used for input validation, invalid input results in a 404 - Not Found response instead of a 400 - Bad Request with an appropriate error message. Route constraints are used to disambiguate similar routes, not to validate the inputs for a particular route.

Reference: Route constraint reference

If you want to check the input by Route constraint, you could implement your own constraint by implementing IRouteConstraint .

1. DateRouteConstraint

    public class DateRouteConstraint : IRouteConstraint { public static string DateRouteConstraintName = "DateRouteConstraint"; public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection) { object dateValue; if (values.TryGetValue("date", out dateValue)) { DateTime date; string[] formats = { "yyyy-MM-dd" }; if (DateTime.TryParseExact(dateValue.ToString(), formats, CultureInfo.InvariantCulture, DateTimeStyles.None, out date)) { return true; } } return false; } }

2. Register DateRouteConstraint

    services.AddRouting(options => { options.ConstraintMap.Add(DateRouteConstraint.DateRouteConstraintName, typeof(DateRouteConstraint)); });

3. Use Case

   [HttpGet("{date:DateRouteConstraint}")] public ActionResult<string> Get(DateTime date) { return Ok(); }

Answer 2

You can't apply a RegularExpression attribute to a DateTime as it's not a string; that attribute is only valid for strings.

You can use a regex route constraint, ie [HttpGet("{date:regex(...)}")] , but in that scenario, you'd be better off using the datetime constraint instead: [HttpGet("{date:datetime}")] .

Answer 3

There is an example here :

https://docs.microsoft.com/en-us/aspnet/web-api/overview/web-api-routing-and-actions/create-a-rest-api-with-attribute-routing#get-books-by-publication-date

With dotnet core 3 i had to escape { and } (make them double) and it simply works :

[HttpGet("{date:datetime:regex(\\d{{4}}-\\d{{2}}-\\d{{2}})}")]
public WeatherForecast GetForecast(DateTime date)
...