Issue when loading the Persona Bar: Not Thread Safe

[berkarslan-xo]

Description of bug

An error, which has the screenshot of it below, is present sometimes several times per day.

Steps to reproduce

Customer has the error frequently; however, unable to reproduce the error on demand, it just happens randomly.

Current result

The following error appears:

2019-04-01 10:04:31,130 [JWWEBSVR21][Thread:44][FATAL] DotNetNuke.Framework.PageBase - An error has occurred while loading page. 
System.InvalidOperationException: Collection was modified; enumeration operation may not execute. 
at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) 
at System.Collections.Generic.List`1.Enumerator.MoveNextRare() 
at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) 
at Evoq.PersonaBar.UI.Controllers.EvoqPersonaBarContainer.Initialize(UserControl personaBarControl) 
at Dnn.PersonaBar.UI.UserControls.PersonaBarContainer.OnInit(EventArgs e) 
at System.Web.UI.Control.InitRecursive(Control namingContainer) 
at System.Web.UI.Control.AddedControl(Control control, Int32 index) 
at DotNetNuke.UI.Skins.Skin.InjectControlPanel() 
at DotNetNuke.UI.Skins.Skin.OnInit(EventArgs e) 
at System.Web.UI.Control.InitRecursive(Control namingContainer) 
at System.Web.UI.Control.AddedControl(Control control, Int32 index) 
at DotNetNuke.Framework.DefaultPage.OnInit(EventArgs e) 
at System.Web.UI.Control.InitRecursive(Control namingContainer) 
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) 

Expected result

This error shouldn't occur.

Screenshots

Error log

Additional context

Affected version

• [x] 9.4.x

Affected browser

• [x] Chrome
• [x] Firefox
• [x] Safari
• [x] Internet Explorer
• [x] Edge

[bdukes]

Do we know what's modifying that list? It seems like the underlying list shouldn't be exposed in the first place.

[berkarslan-xo]

Do we know what's modifying that list? It seems like the underlying list shouldn't be exposed in the first place.

It's coming from cache so that any place that updates the cache for this entity might cause this error but I didn't check the specific locations which update the cache for this entity.

Btw, I have opened PR #1126 for this issue and I put some more info there why this defect occurs.