如何将 DbContext 与 FluentValidator 一起使用

Question

我在尝试编辑用户时收到以下错误。创建或删除用户没有问题。据我了解，fluentvalidator 类中的 uniqueMail 方法和 UserController 类中的 Edit 方法不能很好地结合在一起。

在以下位置抛出异常：

_context.Update(user)

我认为问题是由于 fluentvalidator 类中的 dbcontext 使用不正确造成的。我想说在 fluentvalidator 类中处理上下文有些问题。

您能帮我理解一下哪里出了问题吗？

我还添加了 StartUp 类，以防 FluentValidation 的实现出现问题

错误：

System.InvalidOperationException：无法跟踪实体类型“用户”的实例，因为已经在跟踪具有相同键值 {'Id'} 的另一个实例。附加现有实体时，请确保仅附加一个具有给定键值的实体实例。考虑使用“DbContextOptionsBuilder.EnableSensitiveDataLogging”来查看冲突的键值。

FluentValidatorClass：

using FluentValidation;
using System.Linq;

namespace UserDirectory.Models
{
  public class UserValidator : AbstractValidator<User>
  {
    readonly MvcUserContext _context;
    public UserValidator(MvcUserContext context)
    {
        _context = context;
        RuleFor(x => x.Email).Must(uniqueMail).WithMessage("This email is already in use");
        RuleFor(x => x.Phone).Must(uniquePhone).WithMessage("This phone is already in use");
    }

    private bool uniqueMail(User user, string email)
    {
        var mail = _context.User.Where(x => x.Email.ToLower() == user.Email.ToLower()).SingleOrDefault();

        if (mail == null) return true;
        return mail.Id == user.Id;
    }

    private bool uniquePhone(User user, string phone)
    {
        var phoneNumber = _context.User.Where(x => x.Phone == user.Phone).SingleOrDefault();

        if (phoneNumber == null) return true;
        return phoneNumber.Id == user.Id;
    }
}
}

UserController.cs：

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

namespace UserDirectory.Controllers
{
    public class UsersController : Controller
    {
        private readonly MvcUserContext _context;

        public UsersController(MvcUserContext context)
        {
            _context = context;
        }

        // GET: Users
        public async Task<IActionResult> Index(string sortOrder)
        {

            ViewData["NameSortParm"] = String.IsNullOrEmpty(sortOrder) ? "name_desc" : "";
            ViewData["SurnameSortParm"] = String.IsNullOrEmpty(sortOrder) ? "surname_desc" : "";
            var users = from u in _context.User
                        select u;

            switch (sortOrder)
            {
                case "surname_desc":
                    users = users.OrderByDescending(u => u.Surname);
                    break;
                case "name_desc":
                    users = users.OrderByDescending(u => u.Name);
                    break;
            }

            return View(await users.AsNoTracking().ToListAsync());
        }

        // GET: Users/Details/5
        public async Task<IActionResult> Details(int? id)
        {
            if (id == null)
            {
                return NotFound();
            }

            var user = await _context.User
                .FirstOrDefaultAsync(m => m.Id == id);
            if (user == null)
            {
                return NotFound();
            }

            return View(user);
        }

        // GET: Users/Create
        public IActionResult Create()
        {
            return View();
        }

        // POST: Users/Create
        // To protect from overposting attacks, enable the specific properties you want to bind to.
        // For more details, see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Create([Bind("Id,Name,Surname,Email,BirthDate,Phone,Location")] User user)
        {
            if (ModelState.IsValid)
            {
                _context.Add(user);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View(user);
        }

        // GET: Users/Edit/5
        public async Task<IActionResult> Edit(int? id)
        {
            if (id == null)
            {
                return NotFound();
            }

            var user = await _context.User.FindAsync(id);
            if (user == null)
            {
                return NotFound();
            }
            return View(user);
        }

        // POST: Users/Edit/5
        // To protect from overposting attacks, enable the specific properties you want to bind to.
        // For more details, see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(int id, [Bind("Id,Name,Surname,Email,BirthDate,Phone,Location")] User user)
        {
            if (id != user.Id)
            {
                return NotFound();
            }

            if (ModelState.IsValid)
            {
                try
                {
                    _context.Update(user);
                    await _context.SaveChangesAsync();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!UserExists(user.Id))
                    {
                        return NotFound();
                    }
                    else
                    {
                        throw;
                    }
                }
                return RedirectToAction(nameof(Index));
            }
            return View(user);
        }

        // GET: Users/Delete/5
        public async Task<IActionResult> Delete(int? id)
        {
            if (id == null)
            {
                return NotFound();
            }

            var user = await _context.User
                .FirstOrDefaultAsync(m => m.Id == id);
            if (user == null)
            {
                return NotFound();
            }

            return View(user);
        }

        // POST: Users/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> DeleteConfirmed(int id)
        {
            var user = await _context.User.FindAsync(id);
            _context.User.Remove(user);
            await _context.SaveChangesAsync();
            return RedirectToAction(nameof(Index));
        }

        private bool UserExists(int id)
        {
            return _context.User.Any(e => e.Id == id);
        }
    }
    }

StartUp.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.EntityFrameworkCore;
using FluentValidation.AspNetCore;
using UserDirectory.Models;

namespace UserDirectory
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
            services.AddMvc().AddFluentValidation(fv => fv.RegisterValidatorsFromAssemblyContaining<Models.UserValidator>());
            //services.AddTransient<FluentValidation.IValidator<User>, UserValidator>();

            services.AddDbContext<MvcUserContext>(options =>
                    options.UseSqlite(Configuration.GetConnectionString("MvcUserContext")));
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

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

Answer 1

在验证器上，您从用户中选择并跟踪您要更新的同一实体，这会导致问题。

代替

var mail = _context.User.Where(x => x.Email.ToLower() == user.Email.ToLower()).SingleOrDefault();

写

// The AsNoTracking do not add to the context the entity you select
var mail = _context.User.AsNoTracking().Where(x => x.Email.ToLower() == user.Email.ToLower()).SingleOrDefault();

使用Where 子句，您实现整个实体用户（添加 AsNoTracking 不会将其添加到上下文中），但如果您只想检查实体是否存在，请改用 @987654326 @ 子句转换成这样的 SQL

SELECT TOP 1
FROM TABLE
WHERE Email = 'myEmail'

结果不是用户实体，因此未添加到上下文中。

return _context.User.Any(x => x.Email.ToLower() == user.Email.ToLower());

uniqueMail 和 uniquePhone 必须这样做

Any vs First vs Exists

Any on EF