C#

unsafe delegate void PacketHandler(byte* data, int length);

struct Packet
{
    int type;
    int len;
    PacketHandler func;
}

void CreatePacket()
{
    Packet packet = new Packet
    {
        type = 0x73,
        len = 11,
        func = AuthOK // You only need to specify the name of the function
        // Alternative notation: func = new PacketHandler(AuthOK);
    };
}

unsafe void PacketProcessor(Packet packet)
{
    byte* data = GetPacketData(packet.type);
    packet.func(data, packet.len);
}

unsafe void AuthOK(byte* data, int len) // Matches the PacketHandler delegate signature
{
    // handle packet type 0x73
}

private void txtClientCode_Validated(object sender, EventArgs e)
{
    int rowIndex = -1;
 
    if(!int.TryParse(txtClientCode.Text, out rowIndex))
        return;  // Number cannot be parsed - maybe you could use Validating event instead
 
    DisplayClientInfo(rowIndex);
}
 
private void DisplayClientInfo(int rowIndex)
{
    DataRow row = m_dtClientInfo.Rows[rowIndex];
 
    txtFirstName.Text = (string)row["FirstName"];
    // Fill the rest of the fields here
}

private void txtClientCode_Validated(object sender, EventArgs e)
{
    try
    {
        OleDbDataAdapter l_daCCSearch = new OleDbDataAdapter(
            "SELECT * from ClientFile WHERE ClientCode = '" + txtClientCode.Text + "'", m_connection);
        DataTable l_dtCCSearch = new DataTable();
        l_daCCSearch.Fill(l_dtCCSearch);
        txtClientCode.Text = l_dtCCSearch.Rows[0]["ClientCode"].ToString();
        txtAdress.Text = l_dtCCSearch.Rows[0]["Adress"].ToString();
        txtCity.Text = l_dtCCSearch.Rows[0]["City"].ToString();
        txtCompanyName.Text = l_dtCCSearch.Rows[0]["CompanyName"].ToString();
        txtContactName.Text = l_dtCCSearch.Rows[0]["ContactName"].ToString();
        txtCountry.Text = l_dtCCSearch.Rows[0]["Country"].ToString();
        txtEmail.Text = l_dtCCSearch.Rows[0]["Email"].ToString();
        txtFax.Text = l_dtCCSearch.Rows[0]["FaxNumber"].ToString();
        txtPhone.Text = l_dtCCSearch.Rows[0]["PhoneNumber"].ToString();
        txtPostalCode.Text = l_dtCCSearch.Rows[0]["PostalCode"].ToString();
        txtProvince.Text = l_dtCCSearch.Rows[0]["Province"].ToString();
        txtTaxCode.Text = l_dtCCSearch.Rows[0]["TaxCode"].ToString();
        rtxtNotes.Text = l_dtCCSearch.Rows[0]["Notes"].ToString();

    }
    catch (IndexOutOfRangeException)
    {
        DialogResult result;
        result = MessageBox.Show("Aucune entrée correspondante à votre requête n'a été trouvée.", "Erreur");
        if (result == DialogResult.OK)
        {
            this.ShowCurrentRecord();
        }
    }

}