private void paraEkleToolStripMenuItem_Click(object sender, EventArgs e)
 {
     if (paraYatir == null)
     {
         paraYatir             = new frm_ParaYatir(musteriBanka);
         paraYatir.MdiParent   = this;
         paraYatir.FormClosed += ParaYatir_FormClosed;
         paraYatir.Show();
     }
     else
     {
         paraYatir.Activate();
     }
 }
 private void ParaYatir_FormClosed(object sender, FormClosedEventArgs e)
 {
     paraYatir = null;
 }