public void LoadData()
{
dtKho = new DataTable();
dtKho.Clear();
DataSet ds = nvkho.LayHangHoaDeBan();
dtKho = ds.Tables[0];
dv = new DataView(dtKho);
dgvHangHoa.DataSource = dv;
dgvHangHoa.AutoResizeColumns();
dtKhachHang = new DataTable();
dtKhachHang.Clear();
DataSet dskh = nvkh.LayKH();
dtKhachHang = dskh.Tables[0];
dvKH = new DataView(dtKhachHang);
dgvKhachHang.DataSource = dvKH;
dgvKhachHang.AutoResizeColumns();
dtNhanVien = new DataTable();
dtNhanVien.Clear();
DataSet dsnv = nvnv.LayNV();
dtNhanVien = dsnv.Tables[0];
dvNV = new DataView(dtNhanVien);
dgvNhanVien.DataSource = dvNV;
dgvNhanVien.AutoResizeColumns();
}