For reference object (IsReferenceObject == true), it will try to get its source entity while opening a drawing. This indicates whether the reference object has source entity.
Namespace: Autodesk.Civil.DatabaseServicesAssembly: AeccDbMgd (in AeccDbMgd.dll) Version: 13.2.3892.0
Syntax
C#
public bool IsReferencedSourceExisting { get; }
Visual Basic
Public ReadOnly Property IsReferencedSourceExisting As Boolean
Get
Visual C++
public: property bool IsReferencedSourceExisting { bool get (); }
Examples
API user can get this property to check status of the DRef.
CopyC#

1if (entity.IsReferenceObject && (!entity.IsReferenceValid || !entity.IsReferencedSourceExisting)) 2{ 3 //This reference entity is broken 4}