| Overload | Description | 
|---|---|
| DefaultIfEmpty<TSource>(IEntityQuery<TSource>) | Returns the elements in a sequence or a default valued singleton collection if the sequence is empty. | 
| DefaultIfEmpty<TSource>(IEntityQuery<TSource>,TSource) | Returns the elements in a sequence or a default valued singleton collection if the sequence is empty. | 
Target Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, Windows Vista, Windows Server 2008 family