Linkentity within queryexpression

QueryExpression SrchQry = new QueryExpression();

           SrchQry.EntityName = A.LogicalName;

           SrchQry.ColumnSet = new ColumnSet("a", "b", "c");

           SrchQry.Criteria.AddCondition("country", ConditionOperator.Equal, new string[] { strcodigo });

LinkEntity EntityB = new LinkEntity(A.LogicalName, B.LogicalName, "aid", "aid", JoinOperator.Inner);

           EntityB.Columns = new ColumnSet("a", "b");

           EntityB.EntityAlias = "Entb";

LinkEntity EntityC = new LinkEntity(B.LogicalName, C.LogicalName, "bid", "bid", JoinOperator.Inner);