Conditionally validating portions of an ASP.NET MV

Question

I have certain panels on my page that are hidden under certain circumstances.

For instance I might have a 'billing address' and 'shipping address' and I dont want to validate 'shipping address' if a 'ShippingSameAsBilling' checkbox is checked.

I am trying to use the new DataAnnotations capabilities of ASP.NET MVC 2 (preview 1) to achieve this.

I need to prevent validation of the 'shipping address' when it is not displayed and need to find the way way to achieve this. I am talking mainly server side as opposed to by using jquery.

How can I achieve this? I have had several ideas, related to custom model binding but my current best solution is below. Any feedback on this method?

Answer 1

I created a partial model binder that only validates the keys that were submitted. For security reasons (if I was going to take this a step farther) I'd create a data annotation attribute that marks which fields are allowed to be excluded from a model. Then, OnModelUpdated check field attributes to ensure there is no undesired underposting going on.

public class PartialModelBinder : DefaultModelBinder
{
    protected override void OnModelUpdated(ControllerContext controllerContext, 
        ModelBindingContext bindingContext)
    {
        // default model binding to get errors
        base.OnModelUpdated(controllerContext, bindingContext);

        // remove errors from filds not posted
        // TODO: include request files
        var postedKeys = controllerContext.HttpContext.Request.Form.AllKeys;
        var unpostedKeysWithErrors = bindingContext.ModelState
            .Where(i => !postedKeys.Contains(i.Key))
            .Select(i=> i.Key).ToList();
        foreach (var key in unpostedKeysWithErrors)
        {
            bindingContext.ModelState.Remove(key);
        }
    }    
}