C# Asp.Net MVC 2 Beta ModelBinder更改

我正试图根据MVC2beta中的ValueProvider突破性更改修改以下自定义模型绑定器

protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
      var obj = bindingContext.Model as Core.BusinessBase;
      if (obj != null)
      {
        var errors = from r in obj.BrokenRulesCollection
                     where r.Severity == Validation.RuleSeverity.Error
                     select r;
        foreach (var item in errors)
        {
          bindingContext.ModelState.AddModelError(item.Property, item.Description);
       //Was -> bindingContext.ModelState.SetModelValue(item.Property, bindingContext.ValueProvider[item.Property]);
       bindingContext.ModelState.SetModelValue(item.Property, bindingContext.ValueProvider.GetValue(controllerContext, item.Property));
        }
      }
      else
        base.OnModelUpdated(controllerContext, bindingContext);
}

问题是这一行总是返回为空

BindingContext.ValueProvider.GetValue(controllerContext, item.Property)

有什么想法吗

//DefaultModelBinder.GetModelProperties    
var val = GetModelProperties(controllerContext,bindingContext)[item.Property];

这个怎么样