MVC5 - 如何在DropDownListFor Html帮助器中设置"selectedValue"

Question

正如问题所说:如何在DropDownListFor Html助手中设置selectedValue？

尝试了大多数其他解决方案,但没有工作,这就是为什么我要开一个新问题.

这些都没有帮助:

@Html.DropDownListFor(m => m.TipPopustaId, new SelectList(Model.TipoviDepozita, "Id", "Naziv", 2), htmlAttributes: new { @class = "form-control" })

//Not working with or without cast
@Html.DropDownListFor(m => m.TipPopustaId, new SelectList(Model.TipoviDepozita, "Id", "Naziv", (ProjectName.Models.TipDepozita)Model.TipoviDepozita.Single(x => x.Id == 2)), htmlAttributes: new { @class = "form-control" })
@Html.DropDownListFor(m => m.TipPopustaId, new SelectList(Model.TipoviDepozita, "Id", "Naziv", (ProjectName.Models.TipDepozita)Model.TipoviDepozita.Where(x => x.Id == 2).FirstOrDefault()), htmlAttributes: new { @class = "form-control" })

@Html.DropDownListFor(m => m.TipPopustaId, new SelectList(Model.TipoviDepozita, "Id", "Naziv", new SelectListItem() { Value="2", Selected=true}), htmlAttributes: new { @class = "form-control" })

如果可能的话,我想避免手动创建SelectListItems或ViewModel.

Answer 1

使用DropDownListFor()(或DropDownList())方法绑定到模型属性时,它是设置所选选项的属性的值.

在内部,方法生成它们自己IEnumerable<SelectListItem>的Selected属性并根据属性的值设置属性,因此Selected忽略在代码中设置属性.它唯一被尊重的时候是你没有绑定到模型属性,例如使用

@Html.DropDownList("NotAModelProperty", new SelectList(Model.TipoviDepozita, "Id", "Naziv", 2))

请注意,您可以检查源代码,特别是SelectInternal()和GetSelectListWithDefaultValue()方法,看看它是如何工作的细节.

要在首次呈现视图时显示所选选项,请在将模型传递给视图之前在GET方法中设置属性的值

我还建议您的视图模型包含一个属性,IEnumerable<SelectListItem> TipoviDepozita并SelectList在控制器中生成该属性

var model = new YourModel()
{
    TipoviDepozita = new SelectList(yourCollection, "Id", "Naziv"),
    TipPopustaId = 2 // set the selected option
}
return View(model);

所以观点变成了

@Html.DropDownListFor(m => m.TipPopustaId, Model.TipoviDepozita, new { @class = "form-control" })