private void bar_DSInternet_LinkClicked(object sender, DevExpress.XtraNavBar.NavBarLinkEventArgs e)
 {
     if (formDLInternet == null || formDLInternet.IsDisposed)
     {
         formDLInternet           = new QL_DaiLyInternet();
         formDLInternet.MdiParent = this;
         formDLInternet.Show();
     }
     else
     {
         formDLInternet.Activate();
     }
 }
 private void button_dlInternet_Click(object sender, EventArgs e)
 {
     if (formDLInternet == null || formDLInternet.IsDisposed)
     {
         formDLInternet           = new QL_DaiLyInternet();
         formDLInternet.MdiParent = this;
         formDLInternet.Show();
     }
     else
     {
         formDLInternet.Activate();
     }
 }