private void hesapKapatmaToolStripMenuItem_Click(object sender, EventArgs e)
 {
     if (hesapKapatma == null)
     {
         hesapKapatma             = new frm_HesapKapatma(musteriBanka);
         hesapKapatma.MdiParent   = this;
         hesapKapatma.FormClosed += HesapKapatma_FormClosed;
         hesapKapatma.Show();
     }
     else
     {
         hesapList.Activate();
     }
 }
 private void HesapKapatma_FormClosed(object sender, FormClosedEventArgs e)
 {
     hesapKapatma = null;
 }