Tengo la siguiente consulta SQL y necesito tenerla en LINQ. Intenté varias cosas pero no puedo hacer que funcione.

Aquí está la consulta SQL

SELECT     ST.Description, ST.STId, COUNT(SI.SIId) AS Expr1
FROM         BP INNER JOIN
                      MbrBP ON BP.BPId = MbrBP.BPId INNER JOIN
                      SI ON BP.BPId = SI.BPId RIGHT OUTER JOIN
                      ST ON SI.STId = ST.STId
WHERE     (BP.CountryId = 1) AND (BP.RegionId = 1) AND (MbrBP.MemberId = 1)
      AND (SI.IsActive = 1)
GROUP BY ST.Description, ST.STId
UNION 
SELECT      ST.Description, ST.STId, COUNT(SI.STId) AS Expr1
FROM         SI RIGHT OUTER JOIN
                      ST ON SI.STId = ST.STId
GROUP BY ST.Description, ST.STId