In MVC, I can create a Model Validator which can take Dependencies. I normally use FluentValidation for this. This allows me to, for example, check on account registration tha
This certainly isn't recommended as the class is internal, but you can remove the IModelValidatorCache services in your WebApi config.
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.Services.Clear(Type.GetType("System.Web.Http.Validation.IModelValidatorCache, System.Web.Http"));
}
}