C# ASP.NET Core MVC 应用程序中的视图未获取数据

Question

我正在创建一个 CMS，在其中显示数据库中的信息。这是一个学校数据库。我有一个页面（查看 - 列表），其中有教师列表。当用户单击一位教师时，他们将被定向到另一个页面（查看 - 显示），该页面应该包含有关该特定教师的信息。现在的问题是列表页面正在获取数据并显示它，但显示页面没有获取任何数据并且没有给出任何错误。只是数据没有显示出来。

这是我的代码 -

List.cshtml

:

@model IEnumerable<Cumulative.Models.Teacher>

<h1>This page shows the list of all the teachers.</h1>

@foreach(Cumulative.Models.Teacher CurrentTeacher in Model)
{
    <div><a href="/TeacherPage/Show/@CurrentTeacher.TeacherId">@CurrentTeacher.TeacherFName @CurrentTeacher.TeacherLName</a></div>
}

Show.cshtml

：

@model Cumulative.Models.Teacher
<h1>@Model.TeacherFName @Model.TeacherLName</h1>

TeacherPageController

：

using Microsoft.AspNetCore.Mvc;
using Cumulative.Models;
using Cumulative.Controllers;
using Google.Protobuf.WellKnownTypes;

namespace Cumulative.Controllers
{
    public class TeacherPageController : Controller
    {
        private readonly TeacherAPIController _api;

        public TeacherPageController(TeacherAPIController api)
        {
            _api = api;
        }

        // TeacherPage/List -> A webpage that shows all teachers in the database
        public IActionResult List()
        {
            // creating a variable for the list of teachers
            List<Teacher> Teachers = _api.ListTeachers();

            // direct us to the /Views/TeacherPage/List.cshtml
            return View(Teachers);
        }

        // GET : TeacherPage/Show/{id} -> A webpage that shows a particular teacher in the database matching the given id
        [HttpGet]
        public IActionResult Show(int TeacherId)
        {
            // Creating a Teacher instance for the teacher information received upon inserting the id
            Teacher SelectedTeacher = _api.GiveTeacherInfo(TeacherId);

            return View(SelectedTeacher);
        }
    }
}

TeacherAPIController

：

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Cumulative.Models;
using System;
using MySql.Data.MySqlClient;

namespace Cumulative.Controllers
{
    [Route("api/Teacher")]
    [ApiController]
    public class TeacherAPIController : ControllerBase
    {
        private readonly SchoolDbContext _context;
        // dependency injection of database context
        public TeacherAPIController(SchoolDbContext context)
        {
            _context = context;
        }

        /// <summary>
        /// Returns information about all the teachers
        /// </summary>
        /// <example>
        /// GET api/teacher/GiveTeachersList -> ["","","","",""]
        /// </example>
        /// <returns>
        /// A list of the teachers 
        /// </returns>
        /// 
        [HttpGet]
        [Route(template:"ListTeachers")]
        public List<Teacher> ListTeachers()
        {
            // Create a list of instances of Teachers
            List<Teacher> Teachers = new List<Teacher>();

            // 'using' will close the connection after the code executes
            using (MySqlConnection Connection = _context.AccessDatabase())
            {
                Connection.Open();
                // Establish a new command (query) for our database
                MySqlCommand Command = Connection.CreateCommand();

                //SQL query
                Command.CommandText = "SELECT * FROM teachers";

                // Gather Result Set of Query into a variable
                using (MySqlDataReader ResultSet = Command.ExecuteReader())
                {
                    //Loop Through Each Row of the Result Set
                    while (ResultSet.Read())
                    {
                        int Id = Convert.ToInt32(ResultSet["teacherid"]);
                        string LastName = ResultSet["teacherlname"].ToString();
                        string EmployeeNumber = ResultSet["employeenumber"].ToString();
                        DateTime HireDate = Convert.ToDateTime(ResultSet["hiredate"]);
                        Decimal Salary = Convert.ToDecimal(ResultSet["salary"]);

                        // Add the Teacher Data to the Teachers

                        Teacher CurrentTeacher = new Teacher()
                        {
                            TeacherId = Id,
                            TeacherFName = ResultSet["teacherfname"].ToString(),
                            TeacherLName = LastName,
                            EmployeeNumber = EmployeeNumber,
                            HireDate = HireDate,
                            Salary = Salary
                        };

                        Teachers.Add(CurrentTeacher);
                    }
                }
            }

            return Teachers;
        }

        /// <summary>
        /// Receives a teacher id and returns the associated teacher information
        /// </summary>
        /// <param name="TeacherId">The primary key of the teachers table.</param>
        /// <example>
        /// GET api/teacher/GiveTeacherInfo/5 -> {"":"","":"","":""} 
        /// </example>
        /// <returns>
        /// All the information about one teacher
        /// </returns>
      
        [HttpGet]
        [Route(template:"GiveTeacherInfo/{TeacherId}")]
        public Teacher GiveTeacherInfo(int TeacherId)
        {
            Teacher SelectedTeacher = new Teacher();

            // 'using' will close the connection after the code executes
            using (MySqlConnection Connection = _context.AccessDatabase())
            {
                Connection.Open();
                // Establish a new command (query) for our database
                MySqlCommand Command = Connection.CreateCommand();

                // SQL query
                Command.CommandText = $"SELECT * FROM teachers WHERE teacherid = {TeacherId}";

                // Gather Result Set of Query into the Teacher 
                using (MySqlDataReader ResultSet = Command.ExecuteReader())
                {
                    //Loop Through Each Row of the Result Set
                    while (ResultSet.Read())
                    {
                        SelectedTeacher.TeacherId = Convert.ToInt32(ResultSet["teacherid"]);
                        SelectedTeacher.TeacherFName = ResultSet["teacherfname"].ToString();
                        SelectedTeacher.TeacherLName = ResultSet["teacherlname"].ToString();
                        SelectedTeacher.EmployeeNumber = ResultSet["employeenumber"].ToString();
                        SelectedTeacher.HireDate = Convert.ToDateTime(ResultSet["hiredate"]);
                        SelectedTeacher.Salary = Convert.ToDecimal(ResultSet["salary"]);

                    }
                }
            }

            return SelectedTeacher;
        }
    }
}

Teacher

班级：

namespace Cumulative.Models
{
    public class Teacher
    {
        public int TeacherId { get; set; }

        public string TeacherFName { get; set; }
        public string TeacherLName { get; set; }
        public string EmployeeNumber { get; set; }

        public DateTime HireDate { get; set; }

        public Decimal Salary { get; set; }
    }
}

Answer 1

你的显示页面为空的原因是，你的TeacherId是0。在asp.net core MVC中默认路由如下，但你的路由参数是teacherid，导致modelbinder失败：

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

我建议你可以将你的显示方法修改为以下并再次测试。

public IActionResult Show(int id)
{
    Teacher SelectedTeacher = _api.GiveTeacherInfo(id);
    return View(SelectedTeacher);
}

结果：