我必须添加一个dropdownlist到我现有的项目“moviesite”，我有一个主表“moviestable”添加，编辑和删除电影。现在添加了一个新的表“流派”来添加电影流派。第二个表由两列组成-1，“genreid设置为primarykey和identity，第二列是“name”，由动作、戏剧、喜剧等类型组成，并在主表中添加了一列“genrerefid”，设置为外键。现在我想访问main priject中下拉列表的辅助表列。所以我创建了一个新的模型类“genreclass.cs”，并添加了dbcontext。现在我开始学习如何在模型、控制器和索引中实现它。

NewmovieClass.cs 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.ComponentModel.DataAnnotations;
using Moviesite.Enums;
using System.ComponentModel.DataAnnotations.Schema;

namespace Moviesite.Models
{
    public class NewmovieClass
    {
        [Key]

        public int Movieid { get; set; }

        [Required]
        public string Movietitle { get; set; }

        [Required]
        public string Description { get; set; }

        [Required]
        public string Storyline { get; set; }

        public int Year { get; set; }

        public DateTime Releasedate { get; set; }

        public int Runtime { get; set; }
        [Column(TypeName="nvarchar(50)")]
        public Mvetypenum MovieType { get; set; }

        public int GenreRefId { get; set; }

        [ForeignKey("GenreRefId")]

        public GenreClass Genre { get; set; }

    }
}

GenreClass.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.ComponentModel.DataAnnotations;
using Moviesite.Enums;
using System.ComponentModel.DataAnnotations.Schema;

namespace Moviesite.Models
{
    public class GenreClass
    {
       [Key]
        public int GenreId { get; set; }

        public string Name { get; set; }

        public ICollection<NewmovieClass> newmovieClasses { get; set; }

    }
}

MveController.cs

using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Moviesite.Models;
using Microsoft.EntityFrameworkCore;

namespace Moviesite.Controllers
{
    public class MveController : Controller
    {
        private readonly ApplicationDbContext _db;

        public MveController(ApplicationDbContext db)
        {
            _db = db;
        }
        public IActionResult Index()
        {

            var displaydata = _db.Moviestable.ToList();
            return View(displaydata);

        }

        [HttpGet]

        public async Task<IActionResult> Index (String Mvesearch)

        {
            ViewData["Getmoviedetails"] = Mvesearch;

            var mvequery = from x in _db.Moviestable select x;

            if (!string.IsNullOrEmpty(Mvesearch))

            {
                mvequery = mvequery.Where(x => x.Movietitle.Contains(Mvesearch) || x.Description.Contains(Mvesearch));
            }

            return View(await mvequery.AsNoTracking().ToListAsync());

        }
        public IActionResult Create()

        {
            return View();

        }
        [HttpPost]
        public async Task<IActionResult> Create([Bind("Movieid,Movietitle,Description,Storyline,Year,Releasedate,Runtime,MovieType")] NewmovieClass nmc)
        {

            if (ModelState.IsValid)
          {
                _db.Add(nmc);
                await _db.SaveChangesAsync();
                return RedirectToAction("Index");

            }
            return View(nmc);
        }

        public async Task< IActionResult> Edit(int? id)
        {
            if(id==null)
            {
                return RedirectToAction("Index");
            }
            var getmvedetails = await _db.Moviestable.FindAsync(id);
            return View(getmvedetails);
        }

        [HttpPost]
        public async Task<IActionResult> Edit(NewmovieClass mc)
        {
            if (ModelState.IsValid)
            {
                _db.Update(mc);

                await _db.SaveChangesAsync();

                return RedirectToAction("Index");

            }
            return View(mc);

        }

        public async Task<IActionResult> Details(int? id)
        {
            if (id == null)
            {
                return RedirectToAction("Index");
            }
            var getmvedetails = await _db.Moviestable.FindAsync(id);
            return View(getmvedetails);
        }

        public async Task<IActionResult> Delete(int? id)
        {
            if (id == null)
            {
                return RedirectToAction("Index");
            }
            var getmvedetails = await _db.Moviestable.FindAsync(id);
            return View(getmvedetails);
        }

        [HttpPost]

        public async Task<IActionResult> Delete(int id)
        {

            var getmvedetails = await _db.Moviestable.FindAsync(id);

            _db.Moviestable.Remove(getmvedetails);

            await _db.SaveChangesAsync();

            return RedirectToAction("Index");
        }

    }
}

AppDbcontext

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace Moviesite.Models
{
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        {

        }

        public DbSet<NewmovieClass> Moviestable { get; set; }

      public DbSet<GenreClass> Genre { get; set; }

    }

    }