BeginExecuteReader requires an open and available Connection. The connection's current state is open.

[JeanCollas]

How is this possible?

BeginExecuteReader requires an open and available Connection. The connection's current state is open.
----------------
at System.Data.SqlClient.SqlCommand.<>c.b__122_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 where exception was thrown ---
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot)
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.ExecuteAsync(IRelationalConnection connection, DbCommandMethod executeMethod, IReadOnlyDictionary`2 parameterValues, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Query.AsyncQueryMethodProvider.FastQueryAsyncEnumerable`1.FastQueryAsyncEnumerator.MoveNext(CancellationToken cancellationToken)
at System.Linq.AsyncEnumerable.Aggregate_[TSource,TAccumulate,TResult](IAsyncEnumerable`1 source, TAccumulate seed, Func`3 accumulator, Func`2 resultSelector, CancellationToken cancellationToken)

The caller is

await (from t in DbContext.PlaceAttributes where t.PlaceId == placeId select t).AsNoTracking().ToListAsync();

[smitpatel]

@JeanCollas - I am not able to reproduce this. Can you share a repro project which demonstrate the issue?

[JeanCollas]

Unfortunately the project is probably too complex to share, and the issue does not happen every times, it is random, only a few % of the requests have this issue.

[ajcvickers]

@JeanCollas I have seen this before when multiple threads are using the same DbContext/DbConnection instance concurrently. Both DbContext and DbConnection and other related classes are not thread safe.

[ralmsdeveloper]

@ajcvickers
I do not know if it is useful for you, but I had something identical and solved only with MultipleActiveResultSets =True in my connection string

[JeanCollas]

Thanks, the DbContext is created in the same thread of the execution (it is something like using(new DbContext(dbOptions) ).
However I will check if the concerned connection have the MultipleResultSets activated. :)

[ajcvickers]

@ralmsdeveloper @JeanCollas Setting MultipleActiveResultSets should not resolve this intentionally. It's likely that it is masking a bug in your app code.

[ajcvickers]

EF Team Triage: Closing this issue as the requested additional details have not been provided and we have been unable to reproduce it.

BTW this is a canned response and may have info or details that do not directly apply to this particular issue. While we'd like to spend the time to uniquely address every incoming issue, we get a lot traffic on the EF projects and that is not practical. To ensure we maximize the time we have to work on fixing bugs, implementing new features, etc. we use canned responses for common triage decisions.

[TPIvan]

I had the same issue and it was caused by using
public async void OnGet()
instead of
public async Task OnGet()

[alex-belikov]

I had this issue and I was able to figure it out for my case. It was not related to Entity Framework for me. Here's my code with an issue:

protected SqlConnection Conn()
{
    if (_conn != null) return _conn;

    lock (_lockObject)
    {
        if (_conn != null) return _conn;

        SqlMapper.AddTypeMap(typeof(DateTime), DbType.DateTime2);
        _conn = new SqlConnection(_connectionString);
        _conn.Open();
        return _conn;
    }
}

It might be called by multiple concurrent threads. While first thread was trying to .Open() the connection, the _conn field was already not null. So other threads were using this connection at a time when it was not yet fully opened.

As a solution, I started setting a reference into _conn field when connection is opened, like this:

protected SqlConnection Conn()
{
    if (_conn != null) return _conn;

    lock (_lockObject)
    {
        if (_conn != null) return _conn;

        SqlMapper.AddTypeMap(typeof(DateTime), DbType.DateTime2);
        var conn = new SqlConnection(_connectionString);
        conn.Open();
        return _conn = conn;
    }
}

Hope it helps.

[csstreiser]

I had the same issue and it was caused by using public async void OnGet() instead of public async Task OnGet()

Bless you! this solved my problem