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Question

        public static MvcHtmlString InputFile<TModel, TValue>(this HtmlHelper<TModel> htmlHelper,                      Expression<Func<TModel, TValue>> expression)
        {
            string modelName = ExpressionHelper.GetExpressionText(expression);
            //从Lambda表达式中获取模型对应属性的名称     
            TagBuilder tagBuilder = new TagBuilder("input");
            //设置标签类型为input      
            tagBuilder.Attributes.Add("type", "file");
            //为标签添加type属性及值          
            tagBuilder.Attributes.Add("name", modelName);
            //为标签添加name属性及值          
            tagBuilder.GenerateId(modelName);
            //为标签生成Id，name参数代码Id的值      
            //创建经过HTML加密的字符串         
            //TagRenderMode.SelfClosing枚举值代表当前标签是自动关闭的    
            ModelState modelState;
            if (htmlHelper.ViewData.ModelState.TryGetValue(modelName, out modelState))
            {
                if (modelState.Errors.Count > 0)
                {        //添加错误提示CSS       
                    tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
                }
            }
            return MvcHtmlString.Create(tagBuilder.ToString(TagRenderMode.SelfClosing));
        }
cshtml：
  @Html.InputFile(model => model.FilePath)
control：
  [HttpPost]
  public ActionResult UploadFileCreate(SecUploadFileModel model)问题：  为什么我取的值是model.FilePath="HttpPostedFileWrapper"