由于某種原因，來自我的控制器的 2 個方法觸發了此錯誤：保存背景關系型別“API.Data.DataContext”的更改時，資料庫中發生例外。System.InvalidOperationException：在上一個操作完成之前，在此背景關系上啟動了第二個操作。這通常是由于不同執行緒同時使用同一個 DbContext 實體造成的
我已經嘗試了此執行緒中的所有內容：Entity Framework Core：Entity Framework Core：在上一個操作完成之前在此背景關系中啟動了第二個操作但似乎對我沒有任何作用。
它對我來說不同，因為我不能使用 dbContext 作為 tranziant
該問題發生在 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;
}
}
英雄庫：
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;
}
}
用戶存盤庫
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 宣告
services.AddDbContext<DataContext>(options =>
{
options.UseSqlServer(config.GetConnectionString("DefaultConnection"));
});
It stopped working after I manipulated the Hero repository and I'm not able to figure out what causing it... I have tried everything in this thread: Entity Framework Core: A second operation started on this context before a previous operation completed But nothing seems to work for me. I don't really get why this type of issue happens. Can someone please explain to me what causes that issue? And how can I improve myself to avoid this type of error?
Thanks!!!!
uj5u.com熱心網友回復：
PowerUp 和 DeleteHero 都有以下行：
var user = await this.GetActiveUser();
但是，GetActiveUser 的內容是：
private Task<AppUser> GetActiveUser()
{
var userId = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
var user = this._userRepository.GetUserByIdAsync(userId);
return user;
}
回傳值將始終為空，因為第二行不等待來自 _userRepository 的結果。
這也可能是您的問題的根源，因為在上述第二行完成之前，另一個查詢正在訪問背景關系。
嘗試：
var user = await this._userRepository.GetUserByIdAsync(userId);
您也可以嘗試更改：
return await _context.SaveChangesAsync() > 0;
到
return (await _context.SaveChangesAsync()) > 0;
轉載請註明出處，本文鏈接：https://www.uj5u.com/qiye/364109.html
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