private void AddBtn_Click(object sender, EventArgs e)
        {
            CertificateForm AddCertificate = new CertificateForm();

            if (AddCertificate.ShowDialog() == DialogResult.OK)
            {
                FillCertificatesTable();
            }
        }
        private void EditBtn_Click(object sender, EventArgs e)
        {
            CertificatesListItem CurrentCertificate;

            CurrentCertificate.ID_Certificate = Convert.ToInt32(this.CertificatesTable.SelectedRows[0].Cells[0].Value);
            CurrentCertificate.Name           = Convert.ToString(this.CertificatesTable.SelectedRows[0].Cells[1].Value);
            CurrentCertificate.Number         = Convert.ToString(this.CertificatesTable.SelectedRows[0].Cells[2].Value);
            CurrentCertificate.Begin          = Convert.ToDateTime(this.CertificatesTable.SelectedRows[0].Cells[3].Value);
            CurrentCertificate.End            = Convert.ToDateTime(this.CertificatesTable.SelectedRows[0].Cells[4].Value);
            CurrentCertificate.Organization   = Convert.ToString(this.CertificatesTable.SelectedRows[0].Cells[5].Value);
            CertificateForm EditCertificate = new CertificateForm(CurrentCertificate);

            if (EditCertificate.ShowDialog() == DialogResult.OK)
            {
                FillCertificatesTable();
            }
        }