c# - How to execute FetchXml to get EntityColletion in CRM -

i have fetchxml using need entitycollection. when googled got results using particular service class object follows

fetchexpression fetch = new fetchexpression(fetchxml); entitycollection quickfindviewentitycollection = _service.retrievemultiple(fetch); 

i want know class _service object belongs to. can give me full details of class.

_service instance of class implements iorganizationservice interface.

if code crm plugin or custom workflow, can create instance of context.

if code external application consuming crm services, can create use organizationservice class part of microsoft.xrm.client library.