Dear LLBLGen team,

I'm using the self-servicing package and I'm noticing a issue that occasionally occurs when executing a Linq query with ToListAsync, the weird thing is that the issue occurs occasionally and not with every execution of the query.

Development environment: Oracle Database LLBLGen Runtime version 5.9.1 .NET Framework 4.7.3 LLBLGen designer 5.9 (5.9.0) RTM

Exception:

System.AggregateException: One or more errors have occurred while processing work items. ---> System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
   at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
   at System.Collections.Generic.List`1.System.Collections.IList.get_Item(Int32 index)
   at SD.LLBLGen.Pro.LinqSupportClasses.LinqUtils.GetAllPkFieldsOfEntity(IEntityFieldsCore entityFields)
   at SD.LLBLGen.Pro.LinqSupportClasses.LinqUtils.CreatePkFilterFromEntity(IEntityCore entityInstance, SetAlias objectAlias, ITemplateGroupSpecificCreator creator, Boolean selfServicing, ComparisonOperator operatorToUse)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleBinaryExpressionSeparateOperands(BinaryExpression expressionToHandle, Expression leftSide, Expression rightSide)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleBinaryExpressionBooleanOperator(BinaryExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleDbFunctionCallExpression(DbFunctionCallExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleCtorOrMemberAssignmentParameter(Expression expression)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleMemberAssignment(MemberAssignment assignmentToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleMemberBinding(MemberBinding bindingToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleMemberBindingList(ReadOnlyCollection`1 listToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleMemberInitExpression(MemberInitExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleProjectionExpression(ProjectionExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleJoinExpression(JoinExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleSelectExpression(SelectExpression expressionToHandle, SelectExpression newInstance)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleSelectExpression(SelectExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleSelectExpression(SelectExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleWhereExpression(WhereExpression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.GenericExpressionHandler.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.ExpressionHandlers.QueryExpressionBuilder.HandleExpression(Expression expressionToHandle)
   at SD.LLBLGen.Pro.LinqSupportClasses.LLBLGenProProviderBase.HandleExpressionTree(Expression expression)
   at SD.LLBLGen.Pro.LinqSupportClasses.LLBLGenProProviderBase.<PerformExecuteAsync>d__30.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SD.LLBLGen.Pro.LinqSupportClasses.LLBLGenProProviderBase.<ExecuteAsync>d__29`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SD.LLBLGen.Pro.LinqSupportClasses.LLBLGenProQuery`1.<ExecuteAsync>d__14`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SD.LLBLGen.Pro.LinqSupportClasses.QueryableExtensionMethods.<ToListAsync>d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()

First thing I'd look at is if you have some form of object sharing going on. You're using SelfServicing, so every connection / objects should be standalone by design but there are still things which might look easy enough to share among threads/requests (e.g. in a webapp/api) while it's better to recreate them every time. In these cases it's usually a multi-threading issue.

Is it always with the same query that it fails (when it fails) or every query could potentially fail?