TrackGraph stop tracking if current State is not set, but setting state throw InvalidOperationException

[cdie]

In our situation, we have to work with TrackGraph method because we have mapping between Domain and Persistence layer.

The fact is, in case of update, we look in local tracking entries to retrieve value and update it if necessary

        private void TrackGraph(EntityEntryGraphNode e)
        {
            if (e.Entry.IsKeySet)
            {
                var entry = Context.ChangeTracker.Entries().Where(m => m.Entity.GetType() == e.Entry.Entity.GetType())
                    .FirstOrDefault(m => m.Entity?.Equals(e.Entry.Entity) == true);
                if (entry == null) 
                {
                    e.Entry.State = EntityState.Modified; 
                }
                else
                {
                    var domainValues = GetPropertiesEvaluated(e.Entry.Entity);
                    var currentValues = GetPropertiesEvaluated(entry.Entity);
                    if (domainValues.Except(currentValues).Any())
                    {
                        entry.CurrentValues.SetValues(domainValues);
                        entry.State = EntityState.Modified;
                        if (entry.Entity is DbEntity ent)
                        {
                            ent.EditDate = DateTime.Now;
                        }
                    }
                    else
                    {
                        entry.State = EntityState.Unchanged;
                    }
                }
            }
            else
            {
                e.Entry.State = EntityState.Added;
            }
        }

In case of update, we enter the function with a Detached entity, retrieve the corresponding local instance and then updating it. However, because we're not setting the state of current entering entity in TrackGraph method, the TrackGraph method ends here ( https://github.com/aspnet/EntityFramework/blob/dev/src/EFCore/ChangeTracking/ChangeTracker.cs indicates that State should be different of Detached)

Is this possible to make Callback a Func<EntityEntryGraphNode, bool> to indicate continuation instead of relaying on the State ? Or maybe to have both method signatures ...

In my case, if I set State directly on the e.Entry, I've got and InvalidOperationException because Entity is currently tracked with the same key.

I've already tried to detach local entity, but the thing is, when I set state to my current entity, I have a InvalidOperationException at next node when calling Context.ChangeTracker.Entries().

Further technical details

EF Core version: 1.1.1
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: VS 2017

[ajcvickers]

@cdie We will consider this. As a workaround, you could use IEntityEntryGraphIterator directly. However, this is internal code, so be aware that we may make breaking changes to the API in any release.

[tonysneed]

@ajcvickers I'm thinking that lifting IEntityEntryGraphIterator out of the Internal namespace (see my comment in #10517), might be a better solution that changing the parameter of TrackGraph from Action to Func, since that would be a breaking change on @the API. IEntityEntryGraphIterator.TraverseGraph already has a callback parameter that's a Func<EntityEntryGraphNode, bool>, and there's a TraverseGraphAsync method with the same Func parameter.

[sjb-sjb]

Asking for an improvement in the documentation (https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.changetracking.entityentrygraphnode-1.nodestate?view=efcore-3.1#Microsoft_EntityFrameworkCore_ChangeTracking_EntityEntryGraphNode_1_NodeState).

• Need to state that the callback should return true to continue iteration to nodes reachable from the current node, or false to not iterate on nodes that are reachable from the current node (other than, presumably, nodes that have already been visited).
• Need to explain that the state information is passed to the callback indirectly, in the NodeState property of the EntityEntryGraphNode<TState>.
• Need to explain the difference between the Entry and SourceEntry properties of the EntityEntryGraphNode<TState>.