Can't change Instance's Family. Try changing Instance's Host to a Level first.
Namespace: Autodesk.Revit.DBAssembly: RevitAPI (in RevitAPI.dll) Version: 26.4.0.0 (26.4.0.0)
Syntax
C#
public static FailureDefinitionId CannotChangeInstFam { get; }Property Value
FailureDefinitionId
See Also
Reference