MVC 3 - 访问IEnumerable模型的ModelMetaData？

public static MvcHtmlString DataGrid<T>(this HtmlHelper<T> htmlHelper){}

@model IEnumerable<LogMyAssets.Models.ContactModel>
....
@Html.DataGrid()

var model = (IEnumerable<T>)htmlHelper.ViewData.Model;
var metaData = model.ElementAt(0).GetMetadata();

public static ModelMetadata GetMetadata<TModel>(this TModel model)
{
   return ModelMetadataProviders.Current.GetMetadataForType(null, typeof(TModel));
}

Unable to cast object of type 'System.Collections.Generic.List`1[LMA.Models.ContactModel]' 
to type 'System.Collections.Generic.IEnumerable`1[System.Collections.Generic.IEnumerable`1