Multiplicity constraint violation EF Code-First

Question

i've a problem with using Entity-Framework 6. I've two classes

public class LinkableState : Entity { [Required] public long LinkableId { get; set; } [ForeignKey(@"LinkableId")] public virtual Linkable Linkable { get; set; } public long Counter { get; set; } public string Debug { get; set; } }

and

public class ProcessInstance : InstanceBase<Process> { [Required] public DateTime InstanceStartTime { get; set; } public DateTime? InstanceEndTime { get; set; } public ProcessInstanceState InstanceEndState { get; set; } = ProcessInstanceState.None; public virtual ICollection<LinkableState> LinkableStates { get; set; } = new List<LinkableState>(); public virtual ICollection<LinkableState> LinkableStateTopCounter { get; set; } = new List<LinkableState>(); }

Within my code i like to change ProcessInstance.LinkableStates like in this example (at this time the elements of reachedStates are detached)

using (IDataLayer db = StorageFactory.GetStore()) { ProcessInstance ix = db.GetProcessInstance(processInstanceId); ix.LinkableStates = reachedStates; }

if the db obejct get's disposed and saved i get the error

Multiplicity constraint violated. The role 'ProcessInstance_LinkableStates_Source' of the relationship 'DataLayer.Mssql.DataBase.ProcessInstance_LinkableStates' has multiplicity 1 or 0..1.

I don't know why EF thinks that there is more than 1 relation ? I've checked the EDMX file (reverse from Code-First) which looks like this:

As you can see in the db-entries the key of ProcessInstance_Id (ProcessInstance.LinkableStates) has been nulled even if ID {1, 3} should be set with Process.Id = 1.

This error occured while i switched from

Configuration.ProxyCreationEnabled = true; Configuration.LazyLoadingEnabled = true;

to

Configuration.ProxyCreationEnabled = false; Configuration.LazyLoadingEnabled = false;

At the Moment i've absolute no idea why this error occurs when i switch from lazy to eager loading. i already tried to clear the list and add the new elements manually like:

using (IDataLayer db = StorageFactory.GetStore()) { ProcessInstance ix = db.GetProcessInstance(processInstanceId); ix.LinkableStates.Clear(); foreach (LinkableState e in unvisitedStates) { ix.LinkableStates.Add(e); } }

but this does not change anything.

Do you have any ideas how i can fix this problem ?

thanks in advance :)

Alex · Accepted Answer · 2016-02-05 04:15:50Z

Okay, seems like I've solved the Problem.

I did two things. First, i've added the InverseProperty Annotation to my classes

public class LinkableState : Entity { ... public long? LinkableStatesId { get; set; } public long? LinkableStateTopCounterId { get; set; } [InverseProperty(@"LinkableStates")] [ForeignKey(@"LinkableStatesId")] public virtual ProcessInstance ProcessInstanceLinkableStates { get; set; } [InverseProperty(@"LinkableStateTopCounter")] [ForeignKey(@"LinkableStateTopCounterId")] public virtual ProcessInstance ProcessInstanceLinkableStateTopCounter { get; set; } } public class ProcessInstance : InstanceBase<Process> { ... [InverseProperty(@"ProcessInstanceLinkableStates")] public virtual ICollection<LinkableState> LinkableStates { get; set; } = new List<LinkableState>(); [InverseProperty(@"ProcessInstanceLinkableStateTopCounter")] public virtual ICollection<LinkableState> LinkableStateTopCounter { get; set; } = new List<LinkableState>(); }

and the second thing is that i set the reference Id for LinkableStates by Hand before i save them and check for a already stored version first.

foreach (LinkableState e in copy) { LinkableState tmp = db.GetLinkableState(e.Id) ?? e; tmp.LinkableStatesId = ix.Id; ix.LinkableStates.Add(tmp); }

for now this solved my "Multiplicity constraint violation" error. Hope this will help someone else faceing this problem.

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