private void update()
{
string querry = "select namestaff from [staff] where idstaff > 1 and rolestaff='Doctor'";
c.fill_CB(doctors_CB, querry, "namestaff");
querry = "select idstaff, namestaff from [staff] where idstaff = 1 and rolestaff='Doctor'";
c.fill_txt(principaliddoctor_txt, querry, "idstaff");
c.fill_txt(principalnamedoctor_txt, querry, "namestaff");
}