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我從數據庫填充Dropdownlist，並且想通過設置其「class」屬性以紅色顯示某些元素。所以，我嘗試了很多方法，後來我爲Dropdownlist創建了一個自定義HTML助手。但它沒有任何意義，雖然它似乎添加了class屬性，但此參數無法傳遞到Controller的Razor View。你能幫忙嗎？爲MVC4中的Dropdownlist的某些記錄設置類屬性
MyHelper.cs：
public static MvcHtmlString Custom_DropdownList(this HtmlHelper helper, string name, IEnumerable<SelectListItem> list, object htmlAttributes)
{
TagBuilder dropdown = new TagBuilder("select");
dropdown.Attributes.Add("name", name);
dropdown.Attributes.Add("id", name);
StringBuilder options = new StringBuilder();
foreach (var item in list)
{
options = options.Append("<option value='" + item.Value + "'>" + item.Text + "</option>");
}
dropdown.InnerHtml = options.ToString();
dropdown.MergeAttributes(new RouteValueDictionary(htmlAttributes));
return MvcHtmlString.Create(dropdown.ToString(TagRenderMode.Normal));
}
控制器：
private void PopulateMeetingsDropDownList(object selectedMeetings = null)
{
var meetingsQuery = repository.Meetings
.Join(repository.Cities, m => m.MeetingCityId, c => c.CityID,
(m, c) => new
{
CityID = c.CityID,
CityName = c.CityName,
MeetingDate = m.MeetingStartDate
}
)
.OrderBy(x => x.CityID)
.AsEnumerable()
.Select(
i => new
{
CityID = i.CityID,
Name = string.Format(
"{0} ({1:dd MMMM yyyy})",
i.CityName, i.MeetingDate),
Expired = i.MeetingDate < DateTime.UtcNow
}
).ToList();
var selectItems = new List<SelectListItem>(meetingsQuery.Count);
foreach (var record in meetingsQuery)
{
var item = new SelectListItem
{
Text = record.Name,
Value = record.Name
};
if (record.Expired)
{
item.Attributes.Add("class", "disabled"); //!!! Problem on this line
}
selectItems.Add(item);
}
ViewData["MeetingId"] = new SelectList(meetingsQuery, "CityID", "Name", selectedMeetings);
}
但以這種方法，我做了錯誤「 'System.Web.Mvc.SelectListItem' 後不包含「屬性」的定義，也沒有包含「接受類型的第一個參數」的擴展方法「屬性」。因此，我認爲我需要使用其他屬性或幫助程序將類屬性分配給自定義racords（對「if（record.Expired）」 line）過濾記錄沒有問題。
查看：
@Html.Custom_DropdownList("MeetingId", ViewData["MeetingId"] as SelectList, new { id = "meetingId"})
你能澄清我怎麼提供呢？提前致謝。
這裏是具有兩個類和禁用屬性能力改性殼聚糖代碼：
更新的代碼（用於MyDropdownListFor）：
定製HTML輔助類別：
public static class MyHelpers
{
public class MySelectItem : SelectListItem
{
public string Class { get; set; }
public string Disabled { get; set; }
}
public static MvcHtmlString MyDropdownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IEnumerable<MySelectItem> list, string optionLabel, object htmlAttributes)
{
return MyDropdownList(htmlHelper, ExpressionHelper.GetExpressionText(expression), list, optionLabel, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
}
public static MvcHtmlString MyDropdownList(this HtmlHelper htmlHelper, string name, IEnumerable<MySelectItem> list, string optionLabel, IDictionary<string, object> htmlAttributes)
{
TagBuilder dropdown = new TagBuilder("select");
dropdown.Attributes.Add("name", name);
dropdown.Attributes.Add("id", name);
StringBuilder options = new StringBuilder();
// Make optionLabel the first item that gets rendered.
if (optionLabel != null)
options = options.Append("<option value='" + String.Empty + "'>" + optionLabel + "</option>");
foreach (var item in list)
{
if(item.Disabled == "disabled")
options = options.Append("<option value='" + item.Value + "' class='" + item.Class + "' disabled='" + item.Disabled + "'>" + item.Text + "</option>");
else
options = options.Append("<option value='" + item.Value + "' class='" + item.Class + "'>" + item.Text + "</option>");
}
dropdown.InnerHtml = options.ToString();
dropdown.MergeAttributes(new RouteValueDictionary(htmlAttributes));
return MvcHtmlString.Create(dropdown.ToString(TagRenderMode.Normal));
}
}
控制器：
private void PopulateMeetingsDropDownList(object selectedMeetings = null)
{
var meetingsQuery = repository.Meetings
.Join(repository.Cities, m => m.MeetingCityId, c => c.CityID,
(m, c) => new
{
CityID = c.CityID,
CityName = c.CityName,
MeetingDate = m.MeetingStartDate
}
)
.OrderBy(x => x.CityID)
.AsEnumerable()
.Select(
i => new
{
Value = i.CityID.ToString(),
DisplayValue = string.Format(
"{0} ({1:dd MMMM yyyy})",
i.CityName, i.MeetingDate),
Expired = i.MeetingDate < DateTime.UtcNow
}
).ToList();
var selectItems = new List<MyHelpers.MySelectItem>(meetingsQuery.Count);
foreach (var record in meetingsQuery)
{
var item = new MyHelpers.MySelectItem
{
Text = record.DisplayValue,
Value = record.Value
};
if (record.Expired)
{
item.Class = "disabled";
item.Disabled = "disabled";
}
selectItems.Add(item);
}
ViewBag.MeetingData = selectItems;
}
檢視：
<label>Meeting</label>
@Html.MyDropdownListFor(m => m.MeetingId, ViewBag.MeetingData as List<MyHelpers.MySelectItem>, "---- Select ----",
new { name = "meetingId", id = "meetingId"})
退房這樣的回答：[http://stackoverflow.com/a/7537628/674700](http://stackoverflow.com/a/7537628/674700）。 –
這是一個靜態列表，我認爲該主題與我的問題沒有太大關係。 –
最簡單的方法是連接文本屬性與文本和類的東西像文本＃類，然後在助手分裂它......從代碼的角度來看它是不正確的..但這件事不會改變你現有的代碼...如果將來你想添加更多的屬性或樂趣，那麼斯拉沃的答案是正確的...創建自定義的一個.. –