save changes

MebsisEntities db = new MebsisEntities();

private void button1_Click(object sender, EventArgs e)

{

db.SaveChanges();

CalisanTelefon calisan = new CalisanTelefon();

//calisan.CalisanID = "11111101866";

//calisan.Telefon = "0 532 111 11 11";

foreach (var item in db.Calisan)

{

Random rnd=new Random();

int random = rnd.Next(1000, 10000);

calisan = new CalisanTelefon();

calisan.Telefon = "0 535 422 ";

calisan.CalisanID = item.TCKimlikNo;

calisan.Aciklama = "generated";

db.AddToCalisanTelefon(calisan);

db.SaveChanges();

// MessageBox.Show("ok"+item.Adi);

}

what is wrong with this. It gives error at db.savechanges but I dont think that is related to database :(