Reliably handle ASP.NET MVC model binding errors

Question

I'm developing a REST API using MVC controllers. I'd like to handle all model binding errors and report them to the client in a user-friendly way. In my custom model binders I'm already throwing a special exception that's considered safe by the exception handler and shown to the client.

However, when the default model binder sees an invalid value (say, asdf for an int) it seems to either completely ignore it (if the parameter's not required) or throw a plain ArgumentException (if the parameter is required). Is it possible to reliably handle both cases and get the name of the parameter and the related error, without rewriting the entire binder by hand?

I'd rather not show the ArgumentException as is because it reveals method and namespace names which the client shouldn't have to care about. I'd also rather not parse the ArgumentException message if it's avoidable, and that wouldn't solve the problem with invalid values for non-required parameters being ignored completely.

Did you ever find a good solution? I'm thinking of decorating or subclassing the IModelBinder, but I'd like to know if there is a better way. — Fabian Schmied
– Fabian Schmied, Commented Nov 11, 2016 at 10:22
@FabianSchmied: Unfortunately no. The "Web API" model binder probably has better support for this case - and I don't know about ASP.NET Core. — Matti Virkkunen
– Matti Virkkunen, Commented Nov 14, 2016 at 5:51

Kyle · Accepted Answer · 2013-05-21 17:16:04Z

3

You could implement the IValidatableObject interface on your model. There you can create your own validation logic, replacing the Required attribute validation you currently have.

public class Model : IValidatableObject {
    public int MyIntProperty { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) {
        if (MyIntProperty == 0) {
            yield return new ValidationResult("Please provide a valid value for MyIntProperty.", new[] { "MyIntProperty" });
        }
    }
}

In your controller you can inspect the ModelState.Errors collection to see the validation errors. Also, this will generate the error CSS class on the client side provided you're using a strongly typed view and the HTML form helpers.

edited May 21, 2013 at 17:16

Kyle

1,1721 gold badge8 silver badges23 bronze badges

answered May 15, 2012 at 5:22

Soliah

1,4062 gold badges14 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Reliably handle ASP.NET MVC model binding errors

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related