Already an open DataReader associated with this Connection

[pomelofoundation]

Already an open DataReader associated with this Connection

[matthewjcooper]

Getting the same issue with .Include queries.

[caleblloyd]

I've noticed that it is only affecting me on Has Many includes, when including a relation that is a list of objects. Has One includes seem to work fine.

[yukozh]

It seems that there is no way to enable MultipleActiveResultSets in MySQL, We should refactory the ADO Layer.

[yukozh]

Hi @caleblloyd, @matthewjcooper, just try this:

If you have already installed the pomelo packages: Pomelo.Data.MySql and Pomelo.EntityFrameworkCore.MySql, please remove them and restore again(dotnet restore --no-cache). The packages are located in C:\Users\YOURNAME\.nuget\packages.

I suppose it is works now by a quick fix.

If the error still occurs, please reopen this issue.

[yukozh]

@applenele Can you add this into unit tests?

[tuanbs]

I've been struggling with this issue. Thinking of moving back to SQL Server :(

[mguinness]

@tuanbs Are you using the latest MyGet version? It appears that the MultipleActiveResultSets workaround is no longer needed.

[tuanbs]

@mguinness Yes, I still have this issue after trying get the latest MyGet version. Hope it could be fixed soon. Thanks.

[yukozh]

@tuanbs Could you please open a new issue and provide us the full repro?

[tuanbs]

@yukozh I'll open it soon and reproduce the issue. Actually, I've just tried to run my project with SQL Server and got issue of

System.InvalidCastException: Unable to cast object of type 'System.Data.ProviderBase.DbConnectionClosedConnecting'
 to type 'System.Data.SqlClient.SqlInternalConnectionTds'.

So I guess my code's structure is to blame. I'm going to rewrite it and try with both SQL Server and MySql to see if it can be fixed. Thanks.

[mguinness]

@yukozh It might also be worth creating an issue in the EF Core repo for that System.InvalidCastException in SQL Server. There was a similar error reported in Stack Overflow, are you getting the error because the DI context object has been closed and disposed?