How to add css in a htmlhelper?

In the asp.net mvc 4 developing,I write following code:

@Html.EditorFor(model =>model.CreateTime,new {@class="form-control"}).   

@Html.EditorFor(model =>model.CreateTime,null,new {@class="form-control"})

These two ways didn't work! When I check the html code generated the class element didn't appear.

But when I write these codes,it is fine:

@Html.LabelFor(model =>model.CreateTime,new {@class="form-control"})

So tell me how to do?