You have selected elements that are connected to a Panel object in a Circuit. These elements cannot be removed from the Circuit.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.1.0.0 (26.1.0.34)
Syntax
C#
public static FailureDefinitionId CannotRemoveMembersInCircuitHavingParent { get; }