There is already an open DataReader associated with this Command which must be closed first.

Hi, I am using ASP.NET 5.0 and Linq2Db 3.2.1 for my API. I use SQL Server I am following this guide https://linq2db.github.io/articles/get-started/asp-dotnet-core/index.html I also use services.AddLinqToDbContext to register my DataConnection with the ServiceLifetime is Scoped.

And I got this error when I send 2 requests in the same time. “There is already an open DataReader associated with this Command which must be closed first.”

I think change the ServiceLifetime to Transient is not the good practices. Do you have any ways else or guide doc to solve this issue? Thank you!

For more detail:

fail: LinqToDB.Data.DataConnection[0]
      Error
      Exception: System.InvalidOperationException
      Message  : There is already an open DataReader associated with this Command which must be closed first.
         at System.Data.SqlClient.SqlCommand.<>c.<ExecuteDbDataReaderAsync>b__126_0(Task`1 result)
         at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
         at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
      --- End of stack trace from previous location ---
         at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
      --- End of stack trace from previous location ---
         at LinqToDB.Data.DataConnection.ExecuteReaderAsync(CommandBehavior commandBehavior, CancellationToken cancellationToken)

[sdanyliv]

As I know each request creates scope which equals to creating new DataConnection. Probably problem in you controller, for example missed await, or you have written something like this:

var query1 = ...;
var query2 = ...;

var tasks = new List<Task>{ query1.ToListAsync(), query2.ToListAsync() };

await Task.WhenAll(tasks);

[MaceWindu]

yep, but you need to wait for #2728 to make it work with linq2db