private void Click_Them(object sender, RoutedEventArgs e)
{
string maSV = txtmaSV.Text;
//MessageBox.Show("ma sv: " + maSV);
string hoTen = txthoTen.Text;
string ngaySinh = timengaySinh.Text;
string gioiTinh = txtgioiTinh.Text;
string noiSinh = txtnoiSinh.Text;
string danToc = txtdanToc.Text;
string maLop = txtmaLop.Text;
SV.InsertSinhVien(maSV, hoTen, ngaySinh, gioiTinh, noiSinh, danToc, maLop);
DataView dv = (DataView)dgvSinhVien.ItemsSource;
DataRowView row = dv.AddNew();
row["maSV"] = maSV;
row["hoTen"] = hoTen;
row["ngaySinh"] = ngaySinh;
row["gioiTinh"] = gioiTinh;
row["noiSinh"] = noiSinh;
row["danToc"] = danToc;
row["maLop"] = maLop;
row.EndEdit();
}