默认在列表选择列表中设置选定的值

Question

我想默认在我的选择列表中设置一个选择的值。

这里有这个选择列表：

 @{ List <SelectListItem> dateEcheancierCc = new List <SelectListItem> (); foreach (var dateEch in arrayDateEcheancierCc) { dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch },"Value","Text","Selected-value-by-default"); } <div class="md-select px-0" style="min-width:0px"> @Html.DropDownList("DateEche", dateEcheancierCc, new { @class = "form-conrol" }) </div> } 

在这里，我尝试设置默认情况下选择“默认值”，但对我来说不起作用，为什么？

这里是下拉列表：

  @Html.DropDownList("DateEche", dateEcheancierCc, new { @class = "form-conrol" }) 

Answer 1

dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch },"Value","Text","Selected-value-by-default");

变成这样

dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch, Selected = true });

确保您设置的“ Selected = true”项目是列表中唯一的项目

我不知道您的规则，但您可以尝试这样

例如：我有一个数组{“ Jeffrey”，“ John”，“ Joe”，“ Josh”}，并且我想将Jeffrey设置为默认选择

if (dateEch == "Jeffrey")
    dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch, Selected = true });
else
    dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch });

Answer 2

如果您的视图具有模型，则可以这样使用

                @Html.DropDownListFor(model => model.SelectedId, new SelectList(Model.SelectCollections, "Value", "Text", Model.ValueToBeSelectedInCollection))

Answer 3

在构建SelectListItem时，需要添加Selected=true 。

foreach (var dateEch in arrayDateEcheancierCc)
{
dateEcheancierCc.Add(new SelectListItem() { Text = dateEch, Value = dateEch ,Selected = true });
}

Answer 4

如下所示替换您的DropdownList，

<div class="md-select px-0" style="min-width:0px">
   @Html.DropDownList("DateEche",new SelectList(dateEcheancierCc,"Value","Text","Selected-value-by-default"), new { @class = "form-conrol" })
</div>

并选择列表为

foreach (var dateEch in arrayDateEcheancierCc)
{
dateEcheancierCc.Add(
            new SelectListItem() { Text = dateEch, Value = dateEch }

            );
}

https://dotnetfiddle.net/RFgoD1