Getting "An item with the same key has already been added." when adding entities.

I am getting a sporadic error when I add an entity to an entity collection.  The error is

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System.ArgumentException: An item with the same key has already been added.

   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)

   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)

   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)

   at Mindscape.LightSpeed.LightSpeedContext.(TypeModel )

   at Mindscape.LightSpeed.LightSpeedContext.(Entity )

   at Mindscape.LightSpeed.Entity.GeneratedId()

   at Mindscape.LightSpeed.Entity`1.get_Id()

   at Mindscape.LightSpeed.Entity`1.get_IdInternal()

   at Mindscape.LightSpeed.Model.TypeModel.(Entity )

   at Mindscape.LightSpeed.Entity.get_UniqueId()

   at Mindscape.LightSpeed.UnitOfWorkBase.(Entity )

   at Mindscape.LightSpeed.Entity.AddToUnitOfWorkIdentityMap(Entity )

   at Mindscape.LightSpeed.Entity.SyncUnitOfWork(Entity )

   at Mindscape.LightSpeed.Entity.EntityAddedEvent(Object , EntityEventArgs`1 )

   at Mindscape.LightSpeed.EntityCollection`1.(TEntity )

   at Mindscape.LightSpeed.EntityCollection`1.InsertItem(Int32 index, TEntity item)

   at System.Collections.ObjectModel.Collection`1.Add(T item)

   at CmsModels.Entities.User.AddLog(String action, String details, DateTime actionTime) in D:\dev\dotnet\Projects\CmsWeb\CmsModels\Entities\User.cs:line 68

   at CmsModels.Repositories.UserRepository.AddUserLog(String userName, String action, String details) in D:\dev\dotnet\Projects\CmsWeb\CmsModels\Repositories\UserRepository.cs:line 79

   at CmsWeb.MvcApplication.LogUserAction(String action) in D:\dev\dotnet\Projects\CmsWeb\CmsWeb\Global.asax.cs:line 131

   at CmsWeb.MvcApplication.SaveSessionDetails() in D:\dev\dotnet\Projects\CmsWeb\CmsWeb\Global.asax.cs:line 115

   at CmsWeb.MvcApplication.Session_Start(Object sender, EventArgs e) in D:\dev\dotnet\Projects\CmsWeb\CmsWeb\Global.asax.cs:line 93

   at System.Web.SessionState.SessionStateModule.RaiseOnStart(EventArgs e)

   at System.Web.SessionState.SessionStateModule.CompleteAcquireState()

   at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData)

   at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()

   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

I suspect that it is because my entity (UserLog) uses an indentity column so the Id is 0 when I add it to the entity collection. I am saving the changes imediately after adding the item but the damage may already have been done.

I am unable to reproduce the error reliably, it pops up only when I am not looking for it :(, about once an hour.

Any ideas?

Sean

Looks like a race condition where two threads attempt to cache internal identity generator objects at the same time.  I've committed a fix and it should be in the next nightly.  Thanks for drawing our attention to this, and let us know if it happens again!

Thanks, I will give it a try

I haven't had the issue since upgrading to the nightly.  Thanks.