View没有看到类和公共静态

Question

这是我视图中的帮手。 （我想在下拉列表中列出状态选择）。

@Html.DropDownListFor(model => model.State, SelectListItemHelper.GetStateList())

我收到此错误：  CS0103：当前上下文中不存在名称“SelectListItemHelper”

我把这个类放在我唯一一个拥有所有创建，编辑，删除操作结果的控制器中。我在它下面做了另一个公共课。使用此链接查看我的州信息：How To Create Select List

public class SelectListItemHelper
{
    public static IEnumerable<SelectListItem> GetStateList()
    {
        IList<SelectListItem> items = new List<SelectListItem>
        {
            new SelectListItem() {Text="Alabama", Value="AL"},
            new SelectListItem() { Text="Alaska", Value="AK"},
            new SelectListItem() { Text="Arizona", Value="AZ"},
            new SelectListItem() { Text="Arkansas", Value="AR"},
            new SelectListItem() { Text="California", Value="CA"},
            new SelectListItem() { Text="Colorado", Value="CO"},
            new SelectListItem() { Text="Connecticut", Value="CT"},
            new SelectListItem() { Text="District of Columbia", Value="DC"},
            new SelectListItem() { Text="Delaware", Value="DE"},
            new SelectListItem() { Text="Florida", Value="FL"},
            new SelectListItem() { Text="Georgia", Value="GA"},
            new SelectListItem() { Text="Hawaii", Value="HI"},
            new SelectListItem() { Text="Idaho", Value="ID"},
            new SelectListItem() { Text="Illinois", Value="IL"},
            new SelectListItem() { Text="Indiana", Value="IN"},
            new SelectListItem() { Text="Iowa", Value="IA"},
            new SelectListItem() { Text="Kansas", Value="KS"},
            new SelectListItem() { Text="Kentucky", Value="KY"},
            new SelectListItem() { Text="Louisiana", Value="LA"},
            new SelectListItem() { Text="Maine", Value="ME"},
            new SelectListItem() { Text="Maryland", Value="MD"},
            new SelectListItem() { Text="Massachusetts", Value="MA"},
            new SelectListItem() { Text="Michigan", Value="MI"},
            new SelectListItem() { Text="Minnesota", Value="MN"},
            new SelectListItem() { Text="Mississippi", Value="MS"},
            new SelectListItem() { Text="Missouri", Value="MO"},
            new SelectListItem() { Text="Montana", Value="MT"},
            new SelectListItem() { Text="Nebraska", Value="NE"},
            new SelectListItem() { Text="Nevada", Value="NV"},
            new SelectListItem() { Text="New Hampshire", Value="NH"},
            new SelectListItem() { Text="New Jersey", Value="NJ"},
            new SelectListItem() { Text="New Mexico", Value="NM"},
            new SelectListItem() { Text="New York", Value="NY"},
            new SelectListItem() { Text="North Carolina", Value="NC"},
            new SelectListItem() { Text="North Dakota", Value="ND"},
            new SelectListItem() { Text="Ohio", Value="OH"},
            new SelectListItem() { Text="Oklahoma", Value="OK"},
            new SelectListItem() { Text="Oregon", Value="OR"},
            new SelectListItem() { Text="Pennsylvania", Value="PA"},
            new SelectListItem() { Text="Rhode Island", Value="RI"},
            new SelectListItem() { Text="South Carolina", Value="SC"},
            new SelectListItem() { Text="South Dakota", Value="SD"},
            new SelectListItem() { Text="Tennessee", Value="TN"},
            new SelectListItem() { Text="Texas", Value="TX"},
            new SelectListItem() { Text="Utah", Value="UT"},
            new SelectListItem() { Text="Vermont", Value="VT"},
            new SelectListItem() { Text="Virginia", Value="VA"},
            new SelectListItem() { Text="Washington", Value="WA"},
            new SelectListItem() { Text="West Virginia", Value="WV"},
            new SelectListItem() { Text="Wisconsin", Value="WI"},
            new SelectListItem() { Text="Wyoming", Value="WY"}
        };
        return items;
    }
}