Is it correct way to use ModelState.Remove to deal with ModelState?

Question

Im working on a big MVC3 web application and have an annoyance regarding the ModelState.IsValid method.

ModelState is being used in nearly all of my con

Answer 1

Here's my solution - a RemoveFor() extension method on ModelState, modelled after MVC HTML helpers:

    public static void RemoveFor(this ModelStateDictionary modelState, 
                                         Expression> expression)
    {
        string expressionText = ExpressionHelper.GetExpressionText(expression);

        foreach (var ms in modelState.ToArray())
        {
            if (ms.Key.StartsWith(expressionText + ".") || ms.Key == expressionText)
            {
                modelState.Remove(ms);
            }
        }
    }

Here's how it's used :

if (model.CheckoutModel.ShipToBillingAddress == true) 
{
    // REUSE BILLING ADDRESS FOR SHIPPING ADDRESS
    ShoppingCart.ShippingAddress = ShoppingCart.BillingAddress;

    // REMOVE MODELSTATE ERRORS FOR SHIPPING ADDRESS
    ModelState.RemoveFor(x => model.CheckoutModel.ShippingAddress);
}

So in answer to your question I believe there are definitely use-cases where this is the right way to do it, and a strongly typed helper like this makes it much nicer to look at - and easier to justify if you're concerned about lots of magic strings.