private void btnCustomerAdd_Click_1(object sender, EventArgs e)
        {
            CustomerAddForm customerAddForm = new CustomerAddForm();

            customerAddForm.MdiParent = this.MdiParent;
            customerAddForm.Show();
        }
        private void müşteriEkleToolStripMenuItem_Click(object sender, EventArgs e)
        {
            bool isOpen = false;

            foreach (Form item in this.MdiChildren)
            {
                if (item is CustomerAddForm)
                {
                    isOpen = true;
                }
            }

            if (isOpen == true)
            {
                caf.BringToFront();
            }
            else
            {
                caf           = new CustomerAddForm();
                caf.MdiParent = this;
                caf.Show();
            }
        }