AllowHtml, HttpRequestValidationException and ModelState

I have this viewmodel

public class FooBarViewModel
{
    public string Foo { get; set; }

    [AllowH开发者_如何学Ctml]
    public string Bar { get; set; }
}

Instead of throwing a HttpRequestValidationException if .Foo is submitted with html in it, I want to add a message to ModelState. How could I do that?

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You could decorate the Foo property with the [AllowHtml] attribute as well and inside the controller check whether it contains HTML which would allow you to add a custom error to the model state.

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The exception will be thrown within the DefaultModelBinder at the point where it calls ValueProvider.GetValue.

To change the behaviour to catch the exception and convert it into a ModelState error you would need to extend or replace the DefaultModelBinder.

One possibility is to override BindModel, and at the point where it calls GetValue:

ValueProviderResult valueProviderResult = bindingContext.UnvalidatedValueProvider.GetValue(bindingContext.ModelName, skipValidation: !performRequestValidation);

try and catch the exceptions and call bindingContext.ModelState.AddModelError.

The problem is that the DefaultModelBinder is quite complex so you may need to think carefully about how such a change needs to interact with the rest of the model binding ecosystem.