UpdateModel异常

Question

我正在尝试使用UpdateModel在我的控制器中从FormCollection赋值。控制器看起来像：

public ActionResult EditValues(int id, FormCollection collection)
{
   NamedClass picture = PictureProvider.GetById(id);
   try
   {
      if(ModelState.IsValid)
        {
            UpdateModel(picture, collection);
        }
   }
   catch {}
}

在string UpdateModel(picture, collection);中，我得到了一个ArgumentException，上面写着“已经添加了具有相同键的元素”，仅此而已。Collection和图片有相同的字段..我不想在“集合”中添加任何可能导致这种异常的东西..尝试手动为图片的字段赋值-确定。有没有人见过这样的把戏？提前谢谢你！更新:也许StackTrace会有帮助..

System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   System.Web.Mvc.ModelBindingContext.get_PropertyMetadata()
   System.Web.Mvc.DefaultModelBinder.BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor)
   System.Web.Mvc.DefaultModelBinder.BindProperties(ControllerContext controllerContext, ModelBindingContext bindingContext)
   System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model)
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
   System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
   System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel model, String prefix, String[] includeProperties, String[] excludeProperties, IValueProvider valueProvider)
   System.Web.Mvc.Controller.UpdateModel[TModel](TModel model, String prefix, String[] includeProperties, String[] excludeProperties, IValueProvider valueProvider)
   System.Web.Mvc.Controller.UpdateModel[TModel](TModel model, IValueProvider valueProvider)

Namedclass是：

public class NamedClass
    {
        [Key]
        public virtual int id {get; set;}
        public virtual string username {get; set;}
    }

提供值的视图是：

@model project.Models.NamedClass
@using (Html.BeginForm("EditValues", "PicController", FormMethod.Post))
{
    @Html.HiddenFor(m=>m.id)
    <div class="display-label">@Html.LabelFor(model=>model.username)</div>
    <div class="display-field">
        @Html.EditorFor(model => model.username)
    </div>
    <input type="submit" value="save" />
}

Answer 1

为什么你不能这样做呢。

public ActionResult EditValues(NamedClass model)
{
  if(ModelState.IsValid)
  {
     .. save to db
  }

  return View();
}