Was working on .NET Core application using Entity Framework Core as ORM to database. The application consists of multiple DbContext, public / authorized RESTful API with JWT token authentication.
The request & response flow as below:
Request –> JWT Middleware to grab user object –> Authorization Filter to stop multiple login -> Touch Controller -> Repository -> Execute Query -> Response
An exception occurred while **iterating over** the results of a query for context type. The connection is closed
Check the through LINQ / Lambda query, make sure that has no second query holds queryable object before current queryable object has execute into a list or released.
$One or more errors occurred. (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.
As we know EF Core does not support multiple parallel operations being run on the same DbContext instance
A few troubleshoots can carry out: