Simple code crashes Revit

[Steve_Wellens]

I'm trying to get code from this sample:  http://thebuildingcoder.typepad.com/blog/2010/05/duplicate-legend-component.html  to run.

I am using Revit 2013 so I had to make some changes:

ICollection<ElementId> SelectedIds = m_UIDoc.Selection.GetElementIds();
Group group = m_doc.Create.NewGroup(SelectedIds);

Revit died on the NewGroup call.  There was one ElementId in the selection.

I put an exception handler around it and got this message:

"External component has thrown an exception."

Any ideas? 

Also, is there any other way to clone/copy an Element?

Thanks

[Steve_Wellens]

FYI:  I found the problem was that I was calling the code from a modeless dialog box.  Apparently Revit doesn't like this.

[ollikat]

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@Steve_Wellens wrote:

...Apparently Revit doesn't like this.

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The Essential question is, what did happen to your main thread of the add-in after the modeless dialog was launched? Because that is the only thread you can call Revit API.