Need to allow an action method string parameter to have markup bound to it

I have an action method that takes in a string as its only parameter. The action method transforms it, and returns the result back to the client (this is done on an ajax call). I need to allow markup in the string value. In the past, I've done this by decorating the property on my model with [AllowHtml], but that attribute cannot be used on a parameter and the AllowHtmlAttribute class is sealed, so I cannot inherit from it. I currently have a work around where I've created a model with just one property and decorated it with the aforementioned attribute, and this is working.

I don't think I should have t开发者_如何学编程o jump through that hoop. Is there something I'm missing, or should I make a request to the MVC team to allow this attribute to be used on method parameters?

If you need to allow html input for a particular parameter (opposed to "model property") there's no built-in way to do that because [AllowHtml] only works with models. But you can easily achieve this using a custom model binder:

public ActionResult AddBlogPost(int id, [ModelBinder(typeof(AllowHtmlBinder))] string html)
{
    //...
}

The AllowHtmlBinder code:

public class AllowHtmlBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var request = controllerContext.HttpContext.Request;
        var name = bindingContext.ModelName;
        return request.Unvalidated[name]; //magic happens here
    }
}

Find the complete source code and the explanation in my blog post: https://www.jitbit.com/alexblog/273-aspnet-mvc-allowing-html-for-particular-action-parameters/

Have you looked at ValidateInputAttribute? More info here: http://blogs.msdn.com/b/marcinon/archive/2010/11/09/mvc3-granular-request-validation-update.aspx.