[在使用_context.savechanges()或使用存储库时,我在asp.net core 3.1中遇到了一些问题。
InvalidOperationException: A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of DbContext. For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913.
这里有更多信息出现在浏览器中,
if (bill_VM.Custoemr_selected != null)
{
custId = bill_VM.Custoemr_selected.Id != 0 ? bill_VM.Custoemr_selected.Id : 0;
_shoppingCart.AddCust(custId);
}
//var selectedItem = await _context.Items.Where(p => p.Id == itemId).FirstOrDefaultAsync();
var selectedItem = _itemRepository.GetById(itemId); < ---this point
if (selectedItem != null)
{
_shoppingCart.AddToCart(selectedItem, itemQty, AdjPrice, userid);
}
return RedirectToAction("SalesIndex", "Sales");
我的存储库
public class Repository<T> : IRepository<T> where T : class
{
protected readonly ApplicationDbContext _context;
public Repository(ApplicationDbContext context)
{
_context = context;
}
protected void Save() => _context.SaveChanges();
protected async Task<int> SaveAsync() => await _context.SaveChangesAsync();
........ // some get and create methods are here
public T GetById(int Id)
{
return _context.Set<T>().Find(Id);
}
private bool disposed = false;
protected virtual void Dispose(bool disposing)
{
if (!this.disposed)
{
if (disposing)
{
_context.Dispose();
}
}
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
我的ApplicationDbContext
public class ApplicationDbContext : IdentityDbContext
{
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
: base(options)
{
}
public DbSet<ApplicationUser> ApplicationUsers { get; set; }
public DbSet<ApplicationRole> ApplicationRoles { get; set; }
....... // DbSet
}
服务
services.AddIdentity<ApplicationUser, ApplicationRole>()
.AddEntityFrameworkStores<ApplicationDbContext>();
//start Repo
services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
services.AddTransient<ICategoryRepository, CategoryRepository>();
任何人,请帮助我。运行正常。在我使用事务的multip SaveChanges方法之前。现在我回到以前的代码,仅使用一个savechanges()。之后,我收到此错误=>(开始第二次操作...)。
我可能认为这是由于Async和Await所致。我之前也曾遇到过同样的问题,但我忘记了为此所做的事情。如果可行,请尝试使用同步方法。
您尝试使用ServiceLifetime.Transient
在startup.cs-ConfigureServices中-在配置数据库上下文时
services.AddDbContext<DataContext>(x => x.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")), ServiceLifetime.Transient);