private void btnAdd_Click(object sender, EventArgs e)
 {
     if (String.IsNullOrEmpty(txtName.Text))
     {
         MessageBox.Show("Müşteri ismi boş olamaz.", "Uyarı", MessageBoxButtons.OK, MessageBoxIcon.Warning);
         return;
     }
     try
     {
         DatabaseOperations.AddCustomer(txtName.Text, txtCompany.Text, txtTel.Text);
         MainForm.BtnRefreshPerformClick();
         this.Close();
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message, "Hata", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
 }