asp.net-core 选择标签助手
示例
假设您的视图被强类型化为这样的视图模型
public class CreateProduct
{
public IEnumerable<SelectListItem> Categories { set; get; }
public int SelectedCategory { set; get; }
}在GET操作方法中，您将创建此视图模型的对象，设置Categories属性并将其发送到视图
public IActionResult Create()
{
var vm = new CreateProduct();
vm.Categories= new List<SelectListItem>
{
new SelectListItem {Text = "Books", Value = "1"},
new SelectListItem {Text = "Furniture", Value = "2"}
};
return View(vm);
}在你看来
@model CreateProduct
<form asp-action="create" asp-controller="Home">
<select asp-for="SelectedCategory" asp-items="@Model.Categories">
<option>Select one</option>
</select>
<input type="submit"/>
</form>这将呈现以下标记（仅包括表单/字段的相关部分）
<form action="/Home/create" method="post">
<select data-val="true" id="SelectedCategory" name="SelectedCategory">
<option>Select one</option>
<option value="1">Shyju</option>
<option value="2">Sean</option>
</select>
<input type="submit"/>
</form>在表单提交中获取选定的下拉值
您可以使用与HttpPost操作方法参数相同的视图模型
[HttpPost]
public ActionResult Create(CreateProduct model)
{
//checkmodel.SelectedCategoryvalue
/ /to do : return something
}将一个选项设置为选定的选项
如果要将选项设置为选定选项，则只需设置SelectedCategory属性值即可。
public IActionResult Create()
{
var vm = new CreateProduct();
vm.Categories= new List<SelectListItem>
{
new SelectListItem {Text = "Books", Value = "1"},
new SelectListItem {Text = "Furniture", Value = "2"},
new SelectListItem {Text = "Music", Value = "3"}
};
vm.SelectedCategory= 2;
return View(vm);
}呈现多选下拉列表/列表框
如果要呈现多选下拉列表，只需将用于视图属性的视图模型属性更改为asp-for数组类型即可。
public class CreateProduct
{
public IEnumerable<SelectListItem> Categories { set; get; }
public int[] SelectedCategories { set; get; }
}在视图中
@model CreateProduct
<form asp-action="create" asp-controller="Home" >
<select asp-for="SelectedCategories" asp-items="@Model.Categories">
<option>Select one</option>
</select>
<input type="submit"/>
</form>这将生成具有multiple属性的SELECT元素
<form action="/Home/create" method="post">
<select id="SelectedCategories" multiple="multiple" name="SelectedCategories">
<option>Select one</option>
<option value="1">Shyju</option>
<option value="2">Sean</option>
</select>
<input type="submit"/>
</form>