ASP.NET MVC 2-在IValueProvider上设置值

我正在尝试将我的MVC1项目升级到MVC2RC。我们目前有一个自定义的modelbinder,它向ValueProvider添加项(当它是一个字典时,它就起作用了)。然后我们将其传递给默认的modelbinder。但是,IValueProvider没有add方法,因此该算法不再有效。有人知道在MVC2中向ValueProvider添加值的方法吗?

foreach(string valKey in controllerContext.RequestContext.HttpContext.Request.Form.AllKeys.Where(x => x.StartsWith(valuesToChangePrefix)))
{
    string valName = valKey.Substring(valuesToChangePrefix.Length);

    string myVal = ManipulateValue(bindingContext.ValueProvider.GetValue(valKey).AttemptedValue);

    // This is where I need to add to my value Provider (As you can see I used to just assign a ValueProviderResult
    //bindingContext.ValueProvider = new ValueProviderResult(myVal.Split(','), myVal, bindingContext.ValueProvider.GetValue(valKey).Culture);
}