ROQL querying Custom fields of Contact Object

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Hi 

I have a scenario in my project to fetch the custom fields of Contact Object using Connect API(.NET)

String queryString = "SELECT Contact from Contact C where C.UpdatedTime > '" + timeToday + "' and C.UpdatedTime < '"+ timeNow + "'";

I am using queryObjects to fetch the data 

QueryResultData[] queryData = _service.QueryObjects(clientInfoHeader, queryString, objectTemplates, 10000);

But this query does not return the custom fields in the Contact object.

If I specifically mention "Select c.customfields from Contact" It throws an error "Customfields is not a primary object".

Please suggest a way to fetch customfields. And is it possible to fetch a contact based on Custom fields?