MVC5下拉框绑定的方法（单选）

[Display(Name = "学历")]
 public ICollection<System.Web.Mvc.SelectListItem> asdflist{ get; set; }  //下拉框的类型

[Display(Name = "学历")]
[Required]
public int asdf { get; set; }    //学历这个字段的属性

[Description("学历")]
[LoginAllowView]
 private List<SelectListItem> bind_Education()
{
     StringBuilder sb = new StringBuilder();
     sb.Append(" select id,name ");
     sb.Append(" from Edu_file ");
     DataTable dt = sqlHelp.getData(sb.ToString());//sqlHelp是已经写好的帮助类,便于数据库的操作
     var factorOptions = dt.AsEnumerable().Select(row => new SelectListItem
      {
        Text = row["name"],
        Value = row["id"]
      }).ToList();
      return factorOptions;
}

[Description("学历")]
[LoginAllowView]
private List<SelectListItem> bind_Education()
{
    List<SelectListItem> listItem = new List<SelectListItem>();
    listItem.Add(new SelectListItem { Text = "本科", Value = "1" });
    listItem.Add(new SelectListItem { Text = "硕士", Value = "2" });
     listItem.Add(new SelectListItem { Text = "博士", Value = "3" });
     return listItem;
 }

[Description("我的学历")]
[UIExceptionResult]
 public ActionResult Edu()
{
    var edu= new EduModel();
    edu.asdflist=bind_Education();  //初始化下拉框的值
    return View(edu);
 }

@model RsJob.Web.Models.EduModel  
<div class="form-group">
    @Html.LabelFor(m => m.agj03, new { @class = "col-sm-2 control-label" })
        <div class="col-sm-10">
          @Html.DropDownListFor(model => model.asdf, Model.asdflist, new { @class = "form-control select2", style = "width: 100%;" })
          @Html.ValidationMessageFor(m => m.asdf, "", new { @class = "text-danger" })
        </div>
 </div>