private void btnview_Click(object sender, EventArgs e)
 {
     if (Login.userRole == "tester")
     {
         btnview.Enabled = false;
     }
     else
     {
         if (vb == null)
         {
             View_Bugs vb = new View_Bugs();
             vb.FormClosed += Vb_FormClosed;
             vb.MdiParent   = this;
             vb.Show();
         }
     }
 }
 private void Vb_FormClosed(object sender, FormClosedEventArgs e)
 {
     vb = null;
     //throw new NotImplementedException();
 }