asp.net-mvc 带有默认空选项的 ASP.NET MVC 下拉列表
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ASP.NET MVC dropdown with a default empty option
提问by James Newton-King
Is there a way to include a default empty option (or with text) if there is no selected value for a dropdownlist?
如果下拉列表没有选定的值，有没有办法包含默认的空选项（或带有文本）？
回答by tvanfosson
The below will prepend string.Empty to the SelectList (or IEnumerable) specified in the ViewData["Menu"] item. The select will have id and name MenuID.
下面将在 ViewData["Menu"] 项中指定的 SelectList（或 IEnumerable）前面添加 string.Empty。选择将有 id 和 name MenuID。
<%= Html.DropDownList( "MenuID",
(IEnumerable<SelectListItem>)ViewData["Menu"],
string.Empty ) %>
Documentation: DropDownList method
回答by tiepnv
For Example:
例如：
Controller :
private void InitScreenInfoCollate()
{
IEnumerable<MstBrd> listbrd = ibrandRepository.GetItemsByUsercode("");
ViewBag.Brands = new SelectList(listbrd, "brd_cod", "brd_mei", null);
}
View :
@Html.DropDownList("Brands", null, string.Empty, new { @class = "form-control"})
Result :
结果 ：
回答by PixelPlex
This easy solution worked for my mvc5 project:
这个简单的解决方案适用于我的 mvc5 项目：
in view:
鉴于：
@{
Model.ModelItemsList.Add(new ModelItem{ });
SelectList modelItemSelectList = new SelectList(Model.ModelItemsList, "ModelItemID", "ModelItemName");
}
Just add a new item to the List<>you want to display in your view.
In my case, I added a empty "ModelItem" to my List<ModelItem> ModelItemList. Since my ModelItemID is a Guid, I had to check for Guid.Empty in my controller method and do some code.
Thats all.
只需向List<>要在视图中显示的新项目添加一个新项目。就我而言，我在我的List<ModelItem> ModelItemList. 由于我的 ModelItemID 是一个 Guid，我必须在我的控制器方法中检查 Guid.Empty 并执行一些代码。就这样。
回答by cjbarth
The solution presented here worked very well for me: http://forums.asp.net/t/1142484.aspx/1
这里提出的解决方案对我来说非常有效：http: //forums.asp.net/t/1142484.aspx/1
The basic idea is that you set the AppendDataBoundItemsproperty of your DropDownListto trueand then put an asp:ListItemin the DropDownListand that will become your default item with all the databound items coming after it.
基本思想是，您设置to的AppendDataBoundItems属性，然后将一个in放入，这将成为您的默认项目，所有数据绑定项目都在它之后。DropDownListtrueasp:ListItemDropDownList
