private void btnDeleteCertificate_Click(object sender, EventArgs e) { if (string.IsNullOrEmpty(tbSerialNumber.Text)) { MessageBox.Show("Please enter the serial number of the certificate."); tbSerialNumber.Focus(); return; } Request( delegate { }, delegate { if (!mPenCommV2.IsSupportEncryption) { MessageBox.Show("The pen does not support secure communication."); } if (!mPenCommV2.ReqDeleteCertificate(tbSerialNumber.Text)) { MessageBox.Show("Please check the serial number of the certificate. (Only numbers can be entered.)"); tbSerialNumber.Focus(); } } ); }