ASP.NET MVC - How to handle a string in a model that does not allow nulls?

Question

So I'm a bit new to ASP.NET and MVC. I've got an ASP.NET MVC5 application, using Entity Framework 6. I've generated my models from a SQL Server database, and am so far just using the vanilla index/create/details/edit constructs.

In my models, various fields are marked as "Allow Nulls" and others aren't. While creating a new entry, any type that is, say, an int that is left as null is handled nicely by the ModelState.IsValid check and the @Html.ValidationMessageFor messages.

On one entry test, however, I received a DbEntityValidationException. I used the try/catch from this question to find out that it was one of the string (VARCHAR) fields that was left blank.

I am assuming this is because the string class allows nulls, where as int does not (unless declared as Nullable<type> in the model) thus the controller/model doesn't flag it as invalid.

What would be the easiest way to handle this? Is there a way to decorate the string property in the model so it gets checked as well? Or do I need to go as far as attempting to save, catching the exception, and manually handling the validation messages?

Thanks

Thijs · Accepted Answer · 2014-06-20 13:23:41Z

3

It is possible to decorate your property with a Required-attribute. Mvc wil show an error message when the user is posting a form while this property is empty.

public class TestClassModel
{
    [Required]
    public string RequiredString { get; set; }
}

answered Jun 20, 2014 at 13:23

Thijs

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3 Comments

plast1k Over a year ago

Thank you for the quick response and simple answer!

Nic Over a year ago

What if RequiredString will be null?

Thijs Over a year ago

Then there will be an error in the ModelState and if the validation is turned on, the form on the page won't submit.

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