C# 使用UnitOfWork存储库和带有AutoMapper的服务进行EFCore更新

遵循N层体系结构，我当前在尝试更新实体时遇到问题。在我的控制器中，如果我手动设置属性，则更新工作正常，如果我设置将ViewModel映射到实体的属性，则会生成异常“…无法使用同一关键点跟踪多个对象”。 我怎样才能解决这个问题

这是我的工作单元：

public class UnitOfWork : IUnitOfWork
{
    private readonly CoreContext _context;
    private IGenericRepository<Currency> currencyRepository;

    private static string DataConnectionString => new DatabaseConfiguration().GetDataConnectionString();

    public UnitOfWork(CoreContext context)
    {
        var optionsBuilder = new DbContextOptionsBuilder<CoreContext>();
        optionsBuilder.UseSqlServer(DataConnectionString);
        _context = new CoreContext(optionsBuilder.Options);

    }

    public int Commit()
    {
        return _context.SaveChanges();
    }

    public async Task CommitAsync()
    {
        await _context.SaveChangesAsync();
    }

    private bool disposed = false;

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                _context.Dispose();
            }
        }
        this.disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }


    public IGenericRepository<Currency> CurrencyRepository
    {
        get { return this.currencyRepository ?? (this.currencyRepository = new GenericRepository<Currency>(_context)); }
    }

}


public interface IUnitOfWork : IDisposable
{
    int Commit();
    Task CommitAsync();
    IGenericRepository<Currency> CurrencyRepository { get; }

}

最后，这是我的控制器：

public class CurrencyController : Controller
{
    private readonly ICurrencyService _currencyService;
    private readonly IMapper _mapper;

    public CurrencyController(ICurrencyService currencyService, IMapper mapper)
        : base()
    {
        _currencyService = currencyService;
        _mapper = mapper;
    }


    [HttpPost]
    public ActionResult UpdateCurrency([DataSourceRequest] DataSourceRequest dsRequest, CurrencyViewModel currency)
    {
        if (currency != null && ModelState.IsValid)
        {
            var currencyToUpdate = _currencyService.GetCurrencyById(currency.CurrencyId);

            if (currencyToUpdate != null)
            {
                //UPDATE NOT WORKING
                //currencyToUpdate = _mapper.Map<CurrencyViewModel, Currency>(currency);

                //UPDATE WORKING
                currencyToUpdate.Description = currency.Description;
                currencyToUpdate.Code= currency.Code;
                currencyToUpdate.Symbol = currency.Symbol;

                _currencyService.UpdateCurrency(currencyToUpdate);
                _currencyService.SaveChanges();
            }
        }

        return Json(ModelState.ToDataSourceResult());
    }

公共类CurrencyController:控制器
{
专用只读ICurrencyService\u currencyService；
专用只读IMapper\u映射器；
公共货币控制器（ICurrencyService货币服务，IMapper映射器）
：base（）
{
_currencyService=currencyService；
_映射器=映射器；
}
[HttpPost]
public ActionResult UpdateCurrent（[DataSourceRequest]DataSourceRequest dsRequest，CurrencyViewModel货币）
{
if（currency！=null&&ModelState.IsValid）
{
var currencyToUpdate=\u currencyService.GetCurrencyById（currency.CurrencyId）；
if（currencyToUpdate！=null）
{
//更新不工作
//currencyToUpdate=\u mapper.Map（货币）；
//更新工作
currencyToUpdate.Description=currency.Description；
currencyToUpdate.Code=currency.Code；
currencyToUpdate.Symbol=currency.Symbol；
_currencyService.UpdateCurrency（currencyToUpdate）；
_currencyService.SaveChanges（）；
}
}
返回Json（ModelState.ToDataSourceResult（））；
}

它在您的情况下不起作用，因为您使用的是

IMapper.Map

重载，它创建了

currency

对象的新实例。由于

GetCurrencyById

在成功获取后跟踪实体，您将遇到异常，因为您必须使用相同的键创建实例（一个已经在DbContext中跟踪，另一个是mapper创建的新的）

有两件事可以防止它：

从数据库获取数据时使用

AsNoTracking（）

方法

使用

IMapper.Map

重载，该重载同时获取

currency

的目标和源实例：

_mapper.Map（货币、货币更新）

public class CurrencyService : ICurrencyService
{
    private readonly IUnitOfWork _unitOfWork;

    public void UpdateCurrency(Currency currency)
    {
        _unitOfWork.CurrencyRepository.Update(currency);
    }

    public Currency GetCurrencyById(int Id)
    {
        return _unitOfWork.CurrencyRepository.GetBy(x => x.CurrencyId == Id).Single();

    }

    public int SaveChanges()
    {
        return _unitOfWork.Commit();
    }

}

public interface ICurrencyService 
{
    Currency GetCurrencyById(int Id);
    void UpdateCurrency(Currency currency);

    int SaveChanges();
}

public class CurrencyController : Controller
{
    private readonly ICurrencyService _currencyService;
    private readonly IMapper _mapper;

    public CurrencyController(ICurrencyService currencyService, IMapper mapper)
        : base()
    {
        _currencyService = currencyService;
        _mapper = mapper;
    }


    [HttpPost]
    public ActionResult UpdateCurrency([DataSourceRequest] DataSourceRequest dsRequest, CurrencyViewModel currency)
    {
        if (currency != null && ModelState.IsValid)
        {
            var currencyToUpdate = _currencyService.GetCurrencyById(currency.CurrencyId);

            if (currencyToUpdate != null)
            {
                //UPDATE NOT WORKING
                //currencyToUpdate = _mapper.Map<CurrencyViewModel, Currency>(currency);

                //UPDATE WORKING
                currencyToUpdate.Description = currency.Description;
                currencyToUpdate.Code= currency.Code;
                currencyToUpdate.Symbol = currency.Symbol;

                _currencyService.UpdateCurrency(currencyToUpdate);
                _currencyService.SaveChanges();
            }
        }

        return Json(ModelState.ToDataSourceResult());
    }