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

When your MVC 5 web application page tries to read the database using the Entity Framework in a loop you may get the following error message: InnerException: System.InvalidOperationException HResult=-2146233079 Message=There is already an open DataReader associated with this Command which must be closed first. Source=System.Data This usually happens when a cshtml page receives an IEnumerable<> […]