selecting Null GUID

Question

I am trying  to select Null GUID's uisng linq but all i am getting is an empty result set.

i tired all possible ways of querying it.

var query = from m in datacontext.tablename where m.item_guid == null ||  m.item_guid ==Guid.Empty || m.item_guid.ToString() == null select m;

sql generated (quick watch from VS) 

SELECT  [t0].[item_guid], [t0].[field2]

FROM [dbo].[tablename] AS [t0]

WHERE ([t0].[item_guid] IS NULL) OR ([t0].[item_guid] = @p0) OR ((CONVERT(NVarChar(MAX),[t0].[item_guid])) IS NULL)

 

item_guid is uniquer identifier in SQLSEVER and is returning results when i  query using 'item_guid IS NULL' in sql server.