public void LoadData()
{
dtDocGia = new DataTable();
dtDocGia = docgia.ShowDocGia();
dgvQuanLyTaiLieu.DataSource = dtDocGia;
cbMaDT.DataSource = docgia.getcomboMaDoiTuong();
cbMaDT.DisplayMember = "maDT";
cbMaDT.ValueMember = "maDT";
cbGioiTinh.DataSource = docgia.ShowDocGia();
cbGioiTinh.DisplayMember = "gioiTinh";
cbGioiTinh.ValueMember = "gioiTinh";
}