c# - 无法跟踪实体类型 'Item' 的实例，因为已跟踪具有相同键值 {'Id' } 的另一个实例

Question

我知道已经有人问过这样的问题，但解决方案对我没有帮助。

[Fact]
public async Task UpdateAsync()
{
    string newTitle = "newTitle1";
    int newBrandId = 3;
    var item = await storeContext.Items.AsNoTracking().FirstOrDefaultAsync();
    item.BrandId = newBrandId;
    item.Title = newTitle;
    storeContext.Entry(item).State = EntityState.Detached;
    await service.UpdateAsync(item); // exception inside
    var updatedItem = await storeContext.Items.AsNoTracking().FirstOrDefaultAsync();
    Assert.Equal(newTitle, updatedItem.Title);
    Assert.Equal(newBrandId, updatedItem.BrandId);
}

public async Task UpdateAsync(T entity)
{
    _dbContext.Entry(entity).State = EntityState.Modified; // exception when trying to change the state
    await _dbContext.SaveChangesAsync();
}

Message: System.InvalidOperationException : The instance of entity type 'Item' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.

有趣的是，即使没有从数据库中检索到任何项目，异常也是相同的，就像这样

//var item = await storeContext.Items.AsNoTracking().FirstOrDefaultAsync();
  var item = new Item()
  {
      Id = 1,
      BrandId = newBrandId,
      CategoryId = 1,
      MeasurementUnitId = 1,
      StoreId = 1,
      Title = newTitle
  };

Answer 1

EF core 2.2 也有同样的问题。我从未在其他应用程序中体验过这一点。

最终以某种方式重写了我所有的更新函数:

public bool Update(Entity entity)
{
    try
    {   
       var entry = _context.Entries.First(e=>e.Id == entity.Id);
       _context.Entry(entry).CurrentValues.SetValues(entity);
       _context.SaveChanges();
       return true;
    }
    catch (Exception e)
    {
         // handle correct exception
         // log error
         return false;
    }
}