private void createUserToolStripMenuItem_Click(object sender, EventArgs e)
 {
     if (_create == null)
     {
         _create = new FrmCreateUser {
             MdiParent = this
         };
         _create.FormClosed += _create_FormClosed;
         _create.Show();
         _create.StyleManager = StyleManager;
     }
     else
     {
         _create.Activate();
         _create.WindowState = FormWindowState.Normal;
     }
 }
 private void _create_FormClosed(object sender, FormClosedEventArgs e)
 {
     _create = null;
 }