方法一

Controllers:
var users = GetUsers();

var selectList = new SelectList(users, "Value", "Text", DefaultValue);//如：DefaultValue=users[1].Value

this.ViewData["list"] = selectList;
Views:
<%=Html.DropDownList("List")%>

方法二

Controllers:
List<SelectListItem> List = new List<SelectListItem>();

lList.Add(new SelectListItem { Text = "--请选择--", Value = "",Selected=true });//默认选中项

List.Add(new SelectListItem { Text = "t" + i.ToString(), Value = "v" + i.ToString() });

ViewData["List"] = List;
Views:
<%=Html.DropDownList("List")%>

方法三

Controllers:
List<SelectListItem> List = new List<SelectListItem>();

lList.Add(new SelectListItem { Text = "--请选择--", Value = ""});//默认选中项

List.Add(new SelectListItem { Text = "t" + i.ToString(), Value = "v" + i.ToString() });

ViewData["List"] = List;
ViewData["selected"]=DefaultValue;
Views:
<%=Html.DropDownList("selected",ViewData["List"] as IEnumerable<SelectListItem>)%>