private void btnThemNhaCungCap_Click(object sender, EventArgs e)
{
FrmNhaCungCap frmNhaCungCap = FrmNhaCungCap.Instance;
frmNhaCungCap.MinimizeBox = false;
frmNhaCungCap.FormClosed += FrmNhaCungCap_FormClosed;
((FrmMain)this.ParentForm).TopMost = false;
frmNhaCungCap.ShowDialog();
}