MVC選擇列表的不顯示在下拉

Question

的selectedItem屬性我有下面的代碼在Repository.cs來獲取Timezones

public static IEnumerable<SelectListItem> GetTimeZoneList() 
{ 
    return TimeZoneInfo.GetSystemTimeZones().Select(x => new SelectListItem() 
    { 
     Value = x.Id, 
     Text = x.DisplayName 
    }); 
} 

和我AddEditEmployeeViewModel.cs是如下：

public class AddEditEmployeeViewModel 
{ 
    public string TimeZoneID { get; set; } 
    public SelectList TimeZones { get; set; } 
} 

和Ajax調用，我填型號如下：

public PartialViewResult GetAddEditEmployee(string id) 
{ 
    var model = new AddEditEmployeeViewModel(); 
    model.TimeZones = new SelectList(Repository.GetTimeZoneList(), "Value", "Text"); 
    var employee = (from e in context.tbl_users where e.eid == eid select new { e.fnamae, e.lname, e.account_status, e.preferred_timezone }).FirstOrDefault(); 
    if (employee == null) return PartialView("_AddEditEmployee", model); 
    model.TimeZoneID = employee.preferred_timezone; 
    //model.TimeZoneID will have values like India Standard Time, UTC etc., 
    //..Other properties 
    return PartialView("_AddEditEmp", model); 
} 

夏娃n雖然model.TimeZoneID與獲取的選擇列表具有匹配的值，但它不會將值項保留爲選定狀態。我可以看到SelectList中DB的值。截圖以供參考

這裏是view code

@Html.DropDownListFor(m => m.TimeZoneID, Model.TimeZones, "Select a Timezone", new { @class = "selectpicker", data_width = "100%", }) 

有什麼錯誤我犯在這裏。需要做什麼修改才能從dropdownlist/selectpicker中選擇該項目？

Answer 1

作爲一個規則，我會

model.TimeZones = new SelectList(
    Repository.GetTimeZoneList(), 
    "Value", 
    "Text", 
    model.TimeZoneID); 

更換

model.TimeZones = new SelectList(
    Repository.GetTimeZoneList(), 
    "Value", 
    "Text"); 

基本上，使用overload that takes the selected value as a parameter。你也可以簡單地回到你的時區的對象，而不是SelectListItems的集合：

public static IEnumerable<TimeZone> GetTimeZoneList() 
{ 
    return TimeZoneInfo.GetSystemTimeZones(); 
} 

和

model.TimeZones = new SelectList(
    Repository.GetTimeZoneList(), 
    "ID", 
    "DisplayName", 
    model.TimeZoneID);