在 asp.core razor 页面中设置所选项目

我正在使用 ASP Core Razor 页面。 这是我的 Edit.cshtml.cs：

    [BindProperty]
        public List<Microsoft.AspNetCore.Mvc.Rendering.SelectListItem> CCusers { get; set; }

and here I fill CCusers with data:
 CCusers =new List<Microsoft.AspNetCore.Mvc.Rendering.SelectListItem>() {
                 new Microsoft.AspNetCore.Mvc.Rendering.SelectListItem() { Value = "1", Text = "HR", Selected = true },
                 new Microsoft.AspNetCore.Mvc.Rendering.SelectListItem() { Value = "2", Text = "IT", Selected = false },
                 new Microsoft.AspNetCore.Mvc.Rendering.SelectListItem() { Value = "3", Text = "Account", Selected = false },

            };

在 Razor Page 中，我使用了两种不同的选择：

    <select asp-for="CCusers" asp-items="@Model.CCusers" id="CCusers" multiple="multiple" class="selectpicker"> </select>

//and this:

    @Html.DropDownList("NewSelect", Model.CCusers, new { @class = "selectpicker", @multiple = "multiple" })

这是他们俩的结果：

<select id="CCusers" multiple="multiple" class="selectpicker" name="CCusers"> 
<option value="1">HR</option>
<option value="2">IT</option>
<option value="3">Account</option>
</select>          

<select class="selectpicker" id="NewSelect" multiple="multiple" name="NewSelect">
    <option selected="selected" value="1">HR</option>
    <option value="2">IT</option>
    <option value="3">Account</option>
    </select>

Core Select 没有设置所选项目，而 @Httml.DropDownList 则设置了该项目。 我在第一个选择中缺少什么？

For 选择标签助手，你需要设置asp-for它指定了模型属性名称select元素。

对于您的问题，您需要定义新属性selected CCusers而不是绑定CCusers to asp-for直接地。

您可以参考下面的代码：

Page

public class EditModel : PageModel
{
    [BindProperty]
    public int[] SelectedCCuserIds { get; set; }
    [BindProperty]
    public List<SelectListItem> CCusers { get; set; }
    public void OnGet()
    {
       SelectedCCuserIds = new int[] { 1, 2 };
       CCusers = new List<SelectListItem>() 
          {
            new SelectListItem() { Value = "1", Text = "HR" },
            new SelectListItem() { Value = "2", Text = "IT" },
            new SelectListItem() { Value = "3", Text = "Account" },
          };
        }
        public IActionResult OnPost()
        {
            var result = SelectedCCuserIds;
            return RedirectToAction("OnGet");
        }
    }

View

@page
@model CoreRazor.Pages.EditModel
@{
    ViewData["Title"] = "Edit";
}
<h2>Edit</h2>
<form method="post">
  <select asp-for="@Model.SelectedCCuserIds" asp-items="@Model.CCusers" 
          multiple="multiple" class="selectpicker"> </select>    
          @*@Html.DropDownList("NewSelect", Model.CCusers, new { @class = "selectpicker", 
     @multiple = "multiple" })*@
    <div class="form-group">
        <input type="submit" value="Save" class="btn btn-default" />
    </div>
</form>