Data annotations attributes not working in asp net core

Question

ASP Net core 2.2 application, data annotations attributes [Required] is not working at all. According docs https://learn.microsoft.com/en-ca/dotnet/api/system.componentmodel.dataannotations.requiredattribute?view=netframework-4.7.1#remarks . A validation exception is raised if the property is null, contains an empty string (""), or contains only white-space characters. However, it's not the case in my application.

        [HttpPost]
        public IActionResult TranslateHtml(
            [FromQuery] [Required] int value,
            [FromForm] [Required(AllowEmptyStrings = false)]
            string source)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest();
            }
            return Ok();
        }

When I'm sending request via Postman and do not specify query string value and/or form data source ModelState.IsValid is true. I'm expecting false.

Eugene Zakharov · Accepted Answer · 2019-09-05 14:30:45Z

9

I figured out the source of a problem. I was included .AddMvcCore, and by default it's not including DataAnnotations at all.

services.AddMvcCore()
        .AddDataAnnotations()
        .AddCors()
        .AddJsonFormatters()

I've added .AddDataAnnotations in Startup.cs and it works like a charm.

answered Sep 5, 2019 at 14:30

Eugene Zakharov

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3 Comments

killswitch Over a year ago

I'm using the services.AddControllers() method instead, but my [Required(AllowEmptyStrings = false)] annotation is not working. I also tried calling AddMvcCore().AddDataAnnotations() as well just in case, but it made no difference. Any clue please?

Eugene Zakharov Over a year ago

@killswitch which .net version and application are you using? can you paste a snippet somewhere of your startup class?

killswitch Over a year ago

Never mind, it was a silly mistake from my end. I'm using .Net 6 and the "AddControllers" method internally calls "AddDataAnnotations", so it works automatically. Thanks for your interest!

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