Asp.Net在上一个操作完成之前，在此上下文上启动了第二个操作

Question

由于某种原因，我的控制器中的两个方法触发了此错误：保存上下文类型"API.Data.DataContext"的更改时，数据库中发生异常。System.InvalidOperationException：在上一个操作完成之前，在此上下文上启动了第二个操作。这通常是由不同线程同时使用DbContext 的同一实例引起的

我已经尝试了这个线程中的所有内容：实体框架核心：实体框架内核：在上一个操作完成之前，在这个上下文上开始了第二个操作，但似乎对我无效。

这对我来说是不同的，因为我不能使用dbContext作为transziant

问题发生在PowerUp和DeleteHero方法中

控制器

public class HeroesController : BaseApiController
{
private readonly IUserRepository _userRepository;
public readonly IHeroRepository _heroRepository;
public HeroesController(IUserRepository userRepository, IHeroRepository heroRepository)
{
_userRepository = userRepository;
_heroRepository = heroRepository;
}
[HttpPost("{create}")]
public async Task<ActionResult> CreateHero(RegisterHeroDto registerHeroDto)
{
var user = await this.GetActiveUser();
var existingUserHero = await _heroRepository.IsUserHasHero(user, registerHeroDto.Name);
if (existingUserHero == true) { return BadRequest("You already have a hero with that name"); }
var hero = _heroRepository.HeroBuilder(registerHeroDto, user);
user.Heroes.Add(hero);
if (await _userRepository.SaveAllAsync()) { return Ok(); }
return BadRequest("Failed to create hero");
}
public async Task<ActionResult<IEnumerable<HeroDto>>> GetHeroes()
{
var user = await this.GetActiveUser();
var heroesDto = await _heroRepository.HeroesDtoConverter(user);
return Ok(heroesDto);
}
[HttpPost("powerUp/{id}")]
public async Task<ActionResult> PowerUp(int id)
{
var user = await this.GetActiveUser();
var hero = await _heroRepository.GetHeroById(id);
var canHeroPowerUp = _heroRepository.PowerUpAuthorizer(hero);
if (canHeroPowerUp == false)
{
return BadRequest(hero.Name + " has 0 power-ups left for today");
}
_heroRepository.PowerUp(hero);
var heroesDto = await _heroRepository.HeroesDtoConverter(user);
if (await _userRepository.SaveAllAsync()) { return Ok(); }
return BadRequest("Failed to power up " + hero.Name);
}
[HttpDelete("{id}")]
public async Task<ActionResult> DeleteHero(int id)
{
var user = await this.GetActiveUser();
var hero = await _heroRepository.GetHeroById(id);
_heroRepository.DeleteHero(user, hero);
var heroesDto = await _heroRepository.HeroesDtoConverter(user);
if (await _userRepository.SaveAllAsync()) { return Ok(); }
return BadRequest("Failed to remove hero");
}
private Task<AppUser> GetActiveUser()
{
var userId = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
var user = await this._userRepository.GetUserByIdAsync(userId);
return user;
}
}

英雄库：

public class HeroRepository : ControllerBase, IHeroRepository
{
private readonly DataContext _context;
public readonly IMapper _mapper;
public HeroRepository(DataContext context, IMapper mapper)
{
_context = context;
_mapper = mapper;
}
public async Task<List<Hero>> GetAllHeroes(AppUser user)
{
// refreshPowerUps(user.Heroes.ToList());
// var heroes = user.Heroes
//             .OrderBy(a => a.CurrentPower)
//             .ToList();
var heroes = await _context.Heroes
.Where(a => a.AppUserId == user.Id)
.OrderBy(a => a.CurrentPower)
.ToListAsync();
// var updatedHeroes = refreshPowerUps(heroes);
return heroes;
}
// private async void refreshPowerUps(List<Hero> heroes)
// {
//     foreach (Hero hero in heroes)
//     {
//         if (hero.LastPowerUp.Date.Day != DateTime.Now.Day)
//         {
//             hero.PowerUpsToday = 0;
//         }
//     }
//     await SaveAllAsync();
// }
public async Task<Hero> GetHeroById(int id)
{
return await _context.Heroes
.Where(x => x.Id == id)
.FirstOrDefaultAsync();
}
public Hero HeroBuilder(RegisterHeroDto registerHeroDto, AppUser user)
{
var startingPower = registerHeroDto.Ability == "attacker" ? 100 : 50;
var hero = new Hero
{
Name = registerHeroDto.Name,
Ability = registerHeroDto.Ability,
SuitColors = registerHeroDto.SuitColors,
StartingPower = startingPower,
CurrentPower = startingPower,
AppUserId = user.Id
};
return hero;
}
public async Task<bool> IsUserHasHero(AppUser user, string heroName)
{
if (user.Heroes == null)
{
user.Heroes = new List<Hero>();
}
var existingHero = await _context.Heroes
.Where(x => x.AppUserId == user.Id)
.FirstOrDefaultAsync(x => x.Name.ToLower() == heroName.ToLower());
if (existingHero != null)
{
return true;
}
return false;
}
public bool PowerUpAuthorizer(Hero hero)
{
if (hero.LastPowerUp.Day == DateTime.Now.Day && hero.PowerUpsToday >= 5)
{
return false;
}
return true;
}
public double PowerUp(Hero hero)
{
float powerIncrement = ((new Random().Next(1, 10) * .1f) / 10) + 1;
float newPower = (float)hero.CurrentPower * powerIncrement;
hero.CurrentPower = newPower;
hero.PowerUpsToday++;
hero.LastPowerUp = DateTime.Now;
return newPower;
}
public async Task<bool> SaveAllAsync()
{
return await _context.SaveChangesAsync() > 0;
}
public void DeleteHero(AppUser user, Hero hero)
{
user.Heroes.Remove(hero);
}
public async Task<List<HeroDto>> HeroesDtoConverter(AppUser user)
{
var heroes = await GetAllHeroes(user);
var heroesDto = _mapper.Map<IList<Hero>, IList<HeroDto>>(heroes).ToList();
return heroesDto;
}
}

用户存储库

public class UserRepository : BaseApiController, IUserRepository
{
private readonly DataContext _context;
private readonly IMapper _mapper;
private readonly UserManager<AppUser> _userManager;
public UserRepository(DataContext context, IMapper mapper,
UserManager<AppUser> userManager)
{
_mapper = mapper;
_context = context;
_userManager = userManager;
}
public async Task<AppUser> GetUserByEmailAsync(string email)
{
return await _userManager.Users
.SingleOrDefaultAsync(x => x.Email == email.ToLower());
}
public async Task<AppUser> GetUserByIdAsync(string id)
{
return await _context.Users
.Where(x => x.Id == id)
.Include(a => a.Heroes)
.SingleOrDefaultAsync();
}
public async Task<AppUser> GetUserByUserNameAsync(string userName)
{
return await _userManager.Users
.SingleOrDefaultAsync(x => x.UserName == userName.ToLower());
}
public async Task<bool> SaveAllAsync()
{
return await _context.SaveChangesAsync() > 0;
}
public void Update(AppUser user)
{
_context.Entry(user).State = EntityState.Modified;
}

public async Task<bool> UserExists(string email)
{
return await _userManager.Users.AnyAsync(x => x.Email == email.ToLower());
}
}

dbContext Decartition

services.AddDbContext<DataContext>(options =>
{
options.UseSqlServer(config.GetConnectionString("DefaultConnection"));
});

在我操纵英雄存储库后，它停止了工作，我不知道是什么原因导致的。。。我已经尝试了这个线程中的所有内容：实体框架核心：在上一个操作完成之前，在此上下文上启动了第二个操作但似乎什么都不适合我。我真的不明白为什么会发生这种问题。有人能向我解释一下这个问题的原因吗？我该如何提高自己以避免这种错误？

谢谢！！！！

Answer 1

PowerUp和DeleteHero都有以下行：

var user = await this.GetActiveUser();

但是，GetActiveUser的内容是：

private Task<AppUser> GetActiveUser()
{
var userId = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
var user = this._userRepository.GetUserByIdAsync(userId);
return user;
}

返回的值将始终为null，因为第二行不等待_userRepository的结果。

这也可能是问题的根源，因为在上面的第二行完成之前，另一个查询正在访问上下文。

尝试：

var user = await this._userRepository.GetUserByIdAsync(userId);

您也可以尝试更改：

return await _context.SaveChangesAsync() > 0;

至

return (await _context.SaveChangesAsync()) > 0;

Answer 2

当您收到此错误时，请确保所有可重写的方法都有"等待"；

基本上，我在这些情况下得到这个错误