无法在剃刀页面上获取查询元素

如何解决无法在剃刀页面上获取查询元素

我的页面上有两个查询选择，一个用于客户，另一个用于供应商。为什么我看不到任何元素？

== c# 代码 ==

c# code of page

Pic of VS19 with debugger

在调试器元素中显示见图片编号 2

== 在 Razor 页面==

Pic of HTML Code

很遗憾我看不到任何项目。有什么想法吗？

Layout of page

附上你得到我的代码抱歉只张贴图片

我的 C# 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;
using Microsoft.AspNetCore.Mvc.Rendering;
using WorkCollaboration.Data;
using WorkCollaboration.Models;

namespace WorkCollaboration.Pages.Contacts
{ 
    public class CreateModel : PageModel
    {
        private readonly WorkCollaboration.Data.WorkCollaborationContext _context;

        public CreateModel(WorkCollaboration.Data.WorkCollaborationContext context)
        {
            _context = context;
        }

    public async Task<IActionResult> OnGetAsync()
        {
            CustomerDropDowndisp = await _context.CustomerDropDown.ToListAsync();  // Added for DropDown
            supplierDropDowndisp = await _context.supplierDropDown.ToListAsync();  // Added for DropDown
            return Page();
        }

        [BindProperty]
        public Contact Contact { get; set; }
        public DayOfWeek DayOfWeek { get; set; }
        public IEnumerable<CustomerDropDown> CustomerDropDowndisp { get; set; }
        public IEnumerable<supplierDropDown> supplierDropDowndisp { get; set; }

        // To protect from overposting attacks,enable the specific properties you want to bind to,for
        // more details,see https://aka.ms/RazorPagesCRUD.
        public async Task<IActionResult> OnPostAsync()
        {
            if (!ModelState.IsValid)
            {
                return Page();
            }

            _context.Contact.Add(Contact);
            await _context.SaveChangesAsync();

            return RedirectToPage("/ContactsOverview/Index");
        }
    }
}

这里是我的 Razor 页面 Html

@page 
@model WorkCollaboration.Pages.Contacts.CreateModel

@{
    ViewData["Title"] = "Create";
    ViewData["RandomId"] = Guid.NewGuid().GetHashCode();
}

<h1>Create</h1>
<h4>Contact</h4>
<p>
    <a asp-page="/ContactsOverview/Index">Back to Index</a>
</p>
<hr />
<div class="row">
    <div class="col-md-4">
        <form method="post">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="Contact.ContactId" class="control-label"></label>
                <input asp-for="Contact.ContactId" value='@ViewData["RandomId"]' readonly="readonly" class="form-control" />
                <span asp-validation-for="Contact.ContactId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.LastName" class="control-label"></label>
                <input asp-for="Contact.LastName" class="form-control" />
                <span asp-validation-for="Contact.LastName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.FirstName" class="control-label"></label>
                <input asp-for="Contact.FirstName" class="form-control" />
                <span asp-validation-for="Contact.FirstName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.CustomerId" class="control-label"></label>
                <input asp-for="Contact.CustomerId" class="form-control" />
                <span asp-validation-for="Contact.CustomerId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.CustomerId" class="control-label"></label>
                <select id="CusId" aps-items="@(new SelectList(Model.CustomerDropDowndisp,"CusId","CusName"))">
                    <option value="" selected disabled> -- Select Customer--</option>>
                </select>
                <span asp-validation-for="Contact.CustomerId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.supplierId" class="control-label"></label>
                <input asp-for="Contact.supplierId" class="form-control" />
                <span asp-validation-for="Contact.supplierId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.supplierId" class="control-label"></label>
                <select id="SupId" aps-items="@(new SelectList(Model.supplierDropDowndisp,"SupId","SupName"))">
                    <option value="" selected disabled> -- Select supplier--</option>>
                </select>
                <span asp-validation-for="Contact.supplierId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.PrivateStreet" class="control-label"></label>
                <input asp-for="Contact.PrivateStreet" class="form-control" />
                <span asp-validation-for="Contact.PrivateStreet" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.PrivateStreetNo" class="control-label"></label>
                <input asp-for="Contact.PrivateStreetNo" class="form-control" />
                <span asp-validation-for="Contact.PrivateStreetNo" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.PrivateStreetAdditionalInfo" class="control-label"></label>
                <input asp-for="Contact.PrivateStreetAdditionalInfo" class="form-control" />
                <span asp-validation-for="Contact.PrivateStreetAdditionalInfo" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.PrivateZip" class="control-label"></label>
                <input asp-for="Contact.PrivateZip" class="form-control" />
                <span asp-validation-for="Contact.PrivateZip" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.Privatetown" class="control-label"></label>
                <input asp-for="Contact.Privatetown" class="form-control" />
                <span asp-validation-for="Contact.Privatetown" class="text-danger"></span>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Contact.PrivateCountry,htmlAttributes: new { @class = "form-group" })
                <div class="form-group">
                    @Html.DropDownListFor(model => model.Contact.PrivateCountry,new List<SelectListItem>
                    {
                        new SelectListItem {Text = "CH",Value = "CH",Selected = true },new SelectListItem {Text = "D",Value = "D" },new SelectListItem {Text = "FL",Value = "FL" },},new { @class = "form-control" })
                    @Html.ValidationMessageFor(model => model.Contact.PrivateCountry,"",new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                <label asp-for="Contact.PrivatePhone" class="control-label"></label>
                <input asp-for="Contact.PrivatePhone" class="form-control" />
                <span asp-validation-for="Contact.PrivatePhone" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.BusinessPhone" class="control-label"></label>
                <input asp-for="Contact.BusinessPhone" class="form-control" />
                <span asp-validation-for="Contact.BusinessPhone" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.MobilePhone" class="control-label"></label>
                <input asp-for="Contact.MobilePhone" class="form-control" />
                <span asp-validation-for="Contact.MobilePhone" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.Mail" class="control-label"></label>
                <input asp-for="Contact.Mail" class="form-control" />
                <span asp-validation-for="Contact.Mail" class="text-danger"></span>
            </div>
            <select asp-for="DayOfWeek" asp-items="Html.GetEnumSelectList<DayOfWeek>()">
                <option value="">Choose a day</option>
            </select>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-primary" />
                <a href="/ContactsOverview/Index" class="btn btn-primary">Back to List</a>
            </div>
        </form>
    </div>
</div>

解决方法

在为CustomerDropDownDisp设置数据的那一行打断点。这一定是你的数据库没有数据造成的。你可以按照下面的步骤来检查。

设置断点，然后按IIS Express启动项目：

您可以查看数据库是否不包含 CustomerDropDownDisp、count=0 的任何数据并且剃刀不显示元素：

如果它包含 CustomerDropDownDisp 的数据，则选择列表可以成功呈现：