How to get record into hierarchy class(parent,child,subchild)

var results = from c in db.TableA
              join cn in db.Countries on c.CountryID equals cn.ID
              join ct in db.Cities on c.CityID equals ct.ID
              join sect in db.Sectors on c.SectorID equals sect.ID
              where (c.CountryID == cn.ID) && (c.CityID == ct.ID) && (c.SectorID == company.SectorID) && (company.SectorID == sect.ID)
              select new { country = cn.Name, city = ct.Name, c.ID, c.Name, c.Address1 + c.Address2 + c.Address3, c.PostCode, c.Telephone};
return results.ToList();

SELECT *
FROM (
    SELECT 
        year(invoiceDate) as [year],left(datename(month,invoicedate),3)as [month], 
        InvoiceAmount as Amount 
    FROM Invoice
) as s
PIVOT
(
    SUM(Amount)
    FOR [month] IN (jan, feb, mar, apr, 
    may, jun, jul, aug, sep, oct, nov, dec)
)AS pvt

 SqlConnection conn = new SqlConnection(Sitecore.Configuration.Settings.GetConnectionString("feedback"));
...
Your ADO.net code logic to get data from PIVOT
...
GridView1.DataSource = ds;
GridView1.DataBind();