Why does GroupType.Groups contain ungrouped groups?

[stefanome]

The following code prints the same number twice:

var groupType = group.GroupType;
Debug.Print(groupType.Groups.Size.ToString());
group.UngroupMembers();
Debug.Print(groupType.Groups.Size.ToString());

Is this the correct behavior?

What do I need to do to make sure groupType.Groups always returns the correct GroupSet?

[jeremy_tammik]

Regenerate the model?

https://thebuildingcoder.typepad.com/blog/about-the-author.html#5.33

[stefanome]

Thanks for the tip, but I just tried and regenerating doesn't help.

It looks like I need to end and restart the transaction.

This code shows that GroupType.Groups still reports the ungrouped group after doc.Regenerate() and finally disappears after committing and restarting a new transaction. I tried to get a new reference to the GroupType, hoping that avoiding some caching would help, but it didn't:

tx.Start("Test 1");

var elementIds = new List<ElementId>
{
    Utils.CreateModelLine(new XYZ(0, 0, 0), new XYZ(1, 0, 0), doc).Id,
    Utils.CreateModelLine(new XYZ(0, 1, 0), new XYZ(1, 1, 0), doc).Id,
    Utils.CreateModelLine(new XYZ(0, 2, 0), new XYZ(1, 2, 0), doc).Id,
};
var group1 = doc.Create.NewGroup(elementIds);
var group2 = doc.Create.PlaceGroup(new XYZ(0, 5, 0), group1.GroupType);
var group3 = doc.Create.PlaceGroup(new XYZ(0, 10, 0), group1.GroupType);
Debug.Print(group1.GroupType.Groups.Size.ToString());

group2.UngroupMembers();
Debug.Print(group1.GroupType.Groups.Size.ToString());

doc.Regenerate();
Debug.Print(group1.GroupType.Groups.Size.ToString());

var groupType = new FilteredElementCollector(doc)
    .OfClass(typeof(GroupType))
    .Cast<GroupType>()
    .FirstOrDefault(gt => gt.Name == group1.GroupType.Name);
Debug.Print(groupType.Groups.Size.ToString());

tx.Commit();

tx.Start("Test 2");

Debug.Print(groupType.Groups.Size.ToString());
groupType = new FilteredElementCollector(doc)
    .OfClass(typeof(GroupType))
    .Cast<GroupType>()
    .FirstOrDefault(gt => gt.Name == group1.GroupType.Name);
Debug.Print(groupType.Groups.Size.ToString());

tx.Commit();

I tried using a SubTransaction, but didn't help.

At this point I do have a workaround, but I don't like to create transactions only because I can't rely on GroupType.Groups not reporting ungrouped groups.

Any advice?

[jeremy_tammik]

Glad to hear you were able to discover a workaround.

Yes, committing the transaction is the next level up after regeneration.

Sorry I cannot offer any further suggestions, though.

[GaryOrrMBI · Accepted solution]

"I tried using a SubTransaction, but didn't help.

At this point I do have a workaround, but I don't like to create transactions only because I can't rely on GroupType.Groups not reporting ungrouped groups."

Just firing off the top of my head here but... instead of transactions and subtransactions you might try a transaction group with transactions within it... works just a little differently and perhaps that difference will be a little cleaner in the end...

Just my Two cents, take it for what it's worth 😉

-G

[stefanome]

Using a transaction group seem to be the best workaround. Here are the steps:

transactionGroup.Start
transaction.Start
group.UngroupMemebers
group.GroupType.Groups still contains the ungrouped group
transaction.Commit
group.GroupType.Groups does not contain the ungrouped group

Unfortunately such a workaround cannot be used in a generic case, because wrapping the group.UngroupMembers inside its own transaction only because any following groupType.Groups would return the wrong result is ugly, because it requires any caller to use a transaction group rather than a transaction.

[mhannonQ65N2]

I recently had a somewhat similar problem (working w/ completely different objects though). It seems like in some cases the value returned by a Revit API object's property or method is always the same as when it was first obtained from the API, even after regenerating the model. To resolve this in my case I had to obtain a new copy of the object from the API after regenerating the model (e.g. myElement = myDocument.GetElement(myElementId);). I don't know if this will help in your situation but I hope it does.

[stefanome]

Thanks for the advice. I just tried and in this stale case the cached info sticks around even after getting a new element. Adding these two lines before closing the transaction to my code, still return the wrong value:

group1 = doc.GetElement(group1.Id) as Group;
Debug.Print(groupType.Groups.Size.ToString());

groupType=doc.GetElement(group1.GroupType.Id)as GroupType;
Debug.Print(groupType.Groups.Size.ToString());

[mhannonQ65N2]

Did you regenerate the model before getting the new element?

[stefanome]

Yes, as suggested by Jeremy, but didn't help.

[jeremy_tammik]

Summarised for posterity:

https://thebuildingcoder.typepad.com/blog/2021/05/refreshment-cloud-model-path-angle-and-direction.h...