不能在孔托索大学教程中创建新生

Question

我正在浏览 Contoso University教程，我在第二步中堆放了 crud 。我的代码与模板代码相同。但是，当我试图发布表单时，什么也不会发生。

学生实体：

namespace ContosoUniversity.Models
{
    public class Student
    {
        public int ID { get; set; }
        public string LastName { get; set; }
        public string FirstMidName { get; set; }
        public DateTime EnrollmentDate { get; set; }

        public ICollection<Enrollment> Enrollments { get; set; }
    }
}

Razor页面：

@page
@model ContosoUniversity.Pages.Students.CreateModel

@{
    ViewData["Title"] = "Create";
}

<h1>Create</h1>

<h4>Student</h4>
<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="Student.LastName" class="control-label"></label>
                <input asp-for="Student.LastName" class="form-control" />
                <span asp-validation-for="Student.LastName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Student.FirstMidName" class="control-label"></label>
                <input asp-for="Student.FirstMidName" class="form-control" />
                <span asp-validation-for="Student.FirstMidName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Student.EnrollmentDate" class="control-label"></label>
                <input asp-for="Student.EnrollmentDate" class="form-control" />
                <span asp-validation-for="Student.EnrollmentDate" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-primary" />
            </div>
        </form>
    </div>
</div>

<div>
    <a asp-page="Index">Back to List</a>
</div>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

页面模型：

#nullable disable
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using ContosoUniversity.Data;
using ContosoUniversity.Models;

namespace ContosoUniversity.Pages.Students
{
    public class CreateModel : PageModel
    {
        private readonly SchoolContext _context;

        public CreateModel(SchoolContext context)
        {
            _context = context;
        }

        public IActionResult OnGet()
        {
            return Page();
        }

        [BindProperty]
        public Student Student { get; set; }

        public async Task<IActionResult> OnPostAsync()
        {
            var emptyStudent = new Student();

            if (await TryUpdateModelAsync<Student>(
                emptyStudent,
                "student",   // Prefix for form value.
                s => s.FirstMidName, s => s.LastName, s => s.EnrollmentDate))
            {
                _context.Students.Add(emptyStudent);
                await _context.SaveChangesAsync();
                return RedirectToPage("./Index");
            }

            return Page();
        }
    }
}

学校上下文：

#nullable disable
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using ContosoUniversity.Models;

namespace ContosoUniversity.Data
{
    public class SchoolContext : DbContext
    {
        public SchoolContext (DbContextOptions<SchoolContext> options)
            : base(options)
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Enrollment> Enrollments { get; set; }
        public DbSet<Course> Courses { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Course>().ToTable("Course");
            modelBuilder.Entity<Enrollment>().ToTable("Enrollment");
            modelBuilder.Entity<Student>().ToTable("Student");
        }
    }
}

依赖项注入：

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using ContosoUniversity.Data;
var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();

builder.Services.AddDbContext<SchoolContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("SchoolContext") ?? throw new InvalidOperationException("Connection string 'SchoolContext' not found.")));

builder.Services.AddDatabaseDeveloperPageExceptionFilter();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
}
else
{
    app.UseDeveloperExceptionPage();
    app.UseMigrationsEndPoint();
}

using (var scope = app.Services.CreateScope())
{
    var services = scope.ServiceProvider;

    var context = services.GetRequiredService<SchoolContext>();
    context.Database.EnsureCreated();
    DbInitializer.Initialize(context);
}

app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

sustemant/index.cshtml：

@page
@model ContosoUniversity.Pages.Students.IndexModel

@{
    ViewData["Title"] = "Index";
}

<h1>Index</h1>

<p>
    <a asp-page="Create">Create New</a>
</p>
<table class="table">
    <thead>
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.Student[0].LastName)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Student[0].FirstMidName)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Student[0].EnrollmentDate)
            </th>
            <th></th>
        </tr>
    </thead>
    <tbody>
@foreach (var item in Model.Student) {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.LastName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.FirstMidName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.EnrollmentDate)
            </td>
            <td>
                <a asp-page="./Edit" asp-route-id="@item.ID">Edit</a> |
                <a asp-page="./Details" asp-route-id="@item.ID">Details</a> |
                <a asp-page="./Delete" asp-route-id="@item.ID">Delete</a>
            </td>
        </tr>
}
    </tbody>
</table>

student/index.cshtml.cs：

#nullable disable
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 ContosoUniversity.Data;
using ContosoUniversity.Models;

namespace ContosoUniversity.Pages.Students
{
    public class IndexModel : PageModel
    {
        private readonly ContosoUniversity.Data.SchoolContext _context;

        public IndexModel(ContosoUniversity.Data.SchoolContext context)
        {
            _context = context;
        }

        public IList<Student> Student { get;set; }

        public async Task OnGetAsync()
        {
            Student = await _context.Students.ToListAsync();
        }
    }
}

index.cshtml

@page
@model IndexModel
@{
    ViewData["Title"] = "Home page";
}

<div class="row mb-auto">
    <div class="col-md-4">
        <div class="row no-gutters border mb-4">
            <div class="col p-4 mb-4 ">
                <p class="card-text">
                    Contoso University is a sample application that
                    demonstrates how to use Entity Framework Core in an
                    ASP.NET Core Razor Pages web app.
                </p>
            </div>
        </div>
    </div>
    <div class="col-md-4">
        <div class="row no-gutters border mb-4">
            <div class="col p-4 d-flex flex-column position-static">
                <p class="card-text mb-auto">
                    You can build the application by following the steps in a series of tutorials.
                </p>
                <p>
@*                    <a href="https://learn.microsoft.com/aspnet/core/data/ef-rp/intro" class="stretched-link">See the tutorial</a>
*@                </p>
            </div>
        </div>
    </div>
    <div class="col-md-4">
        <div class="row no-gutters border mb-4">
            <div class="col p-4 d-flex flex-column">
                <p class="card-text mb-auto">
                    You can download the completed project from GitHub.
                </p>
                <p>
@*                    <a href="https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/data/ef-rp/intro/samples" class="stretched-link">See project source code</a>
*@                </p>
            </div>
        </div>
    </div>
</div>

index.cshtml.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace ContosoUniversity.Pages
{
    public class IndexModel : PageModel
    {
        private readonly ILogger<IndexModel> _logger;

        public IndexModel(ILogger<IndexModel> logger)
        {
            _logger = logger;
        }

        public void OnGet()
        {

        }
    }
}

这里没有出现。另外，我安装了所有必需的nuget软件包

sreenshots：

创建学生页面

ssox

devtools错误：

devtools错误

Answer 1

一个更详细的答案，可能会帮助其他有这个问题的人：

问题是，

public ICollection<Enrollment> Enrollments { get; set; }

当用户创建新学生时，学生实体的注册导航属性“注册”为无效。这导致了无效的模型状态。为了消除此问题，您可以从contosouniversity.csproj文件中删除行＆lt;如果您不想在整个项目中启用无效的参考类型，则可以通过添加“？”来更改导航属性。如下：

public ICollection<Enrollment>? Enrollments { get; set; }

Answer 2

问题是我没有从contosouniversity.csproj文件中删除启用