Imports System
Imports System.Windows.Forms

Imports Xceed.FileSystem
Imports Xceed.Ftp

Private Shared Sub CertificateReceivedExample(ByVal form As Form)
  Using connection As New FtpConnection("ftp.myplace.com", 990, "ftp_user_name", "ftp_user_name's remote password", AuthenticationMethod.Tls, VerificationFlags.None, Nothing, DataChannelProtection.Private, True)
    ' Subscribe to the CertificateReceived event to consult the certificate sent by the server
    AddHandler connection.CertificateReceived, AddressOf OnCertificateReceived

    ' Make events be redirected to the main UI thread and DoEvents() called in the background
    connection.SynchronizingObject = form

    Dim folder As New FtpFolder(connection)

    For Each item As FileSystemItem In folder.GetItems(True)
      Console.WriteLine(item.FullName)
    Next item
  End Using
End Sub

Private Sub OnCertificateReceived(ByVal sender As Object, ByVal e As CertificateReceivedEventArgs)
  ' Here, we should be in the main UI thread since we set the SynchronizingObject property.
  ' We can therefore perform UI operations here without worry.

  ' The Status argument property tells you if the server certificate was accepted
  ' based on the VerificationFlags you provided.
  If e.Status <> VerificationStatus.ValidCertificate Then
    Console.WriteLine("The server certificate is invalid: {0}", e.Status.ToString())
    Console.WriteLine(e.ServerCertificate.ToString())
    ' You have three choices here:
    '
    '  1) Refuse the certificate by setting e.Action to VerificationAction.Reject,
    '      thus making the authentication fail. This is e.Action's default value
    '      when the server certificate isn't valid.
    '
    '  2) Set e.Flags to less restrictive criterion and ask the library to
    '      validate the certificate again by setting e.Action to
    '      VerificationAction.VerifyAgain.
    '
    '  3) Force the library to accept this certificate by setting e.Action to
    '      VerificationAction.Accept.
    '
    ' We'll do #1 or #3, depending on the user's answer.
    Console.WriteLine("Do you want to accept this certificate anyway? [Y/N]")

    Dim answer As Integer = Console.Read()
    If (answer = AscW("y"c)) OrElse (answer = AscW("Y"c)) Then
      e.Action = VerificationAction.Accept
    End If
  Else
    ' e.Action's default value is VerificationAction.Accept
    Console.WriteLine("Valid certificate received from server.")
  End If
End Sub

using System;
using System.Windows.Forms;

using Xceed.FileSystem;
using Xceed.Ftp;

private static void CertificateReceivedExample( Form form )
{
  using( FtpConnection connection = new FtpConnection( "ftp.myplace.com", 990,
                                                      "ftp_user_name",
                                                      "ftp_user_name's remote password",
                                                      AuthenticationMethod.Tls,
                                                      VerificationFlags.None,
                                                      null,
                                                      DataChannelProtection.Private,
                                                      true ) )
  {
    // Subscribe to the CertificateReceived event to consult the certificate sent by the server
    connection.CertificateReceived += new CertificateReceivedEventHandler( OnCertificateReceived );

    // Make events be redirected to the main UI thread and DoEvents() called in the background
    connection.SynchronizingObject = form;

    FtpFolder folder = new FtpFolder( connection );

    foreach( FileSystemItem item in folder.GetItems( true ) )
    {
      Console.WriteLine( item.FullName );
    }
  }
}
 
private void OnCertificateReceived( object sender, CertificateReceivedEventArgs e )
{
  /* Here, we should be in the main UI thread since we set the SynchronizingObject property.
  * We can therefore perform UI operations here without worry. */

  // The Status argument property tells you if the server certificate was accepted
  // based on the VerificationFlags you provided.
  if( e.Status != VerificationStatus.ValidCertificate )
  {
    Console.WriteLine( "The server certificate is invalid: {0}", e.Status.ToString() );
    Console.WriteLine( e.ServerCertificate.ToString() );
    // You have three choices here:
    //
    //  1) Refuse the certificate by setting e.Action to VerificationAction.Reject,
    //      thus making the authentication fail. This is e.Action's default value
    //      when the server certificate isn't valid.
    //
    //  2) Set e.Flags to less restrictive criterion and ask the library to
    //      validate the certificate again by setting e.Action to
    //      VerificationAction.VerifyAgain.
    //
    //  3) Force the library to accept this certificate by setting e.Action to
    //      VerificationAction.Accept.
    //
    // We'll do #1 or #3, depending on the user's answer.
    Console.WriteLine( "Do you want to accept this certificate anyway? [Y/N]" );

    int answer = Console.Read();
    if( ( answer == 'y' ) || ( answer == 'Y' ) )
    {
      e.Action = VerificationAction.Accept;
    }
  }
  else
  {
    // e.Action's default value is VerificationAction.Accept
    Console.WriteLine( "Valid certificate received from server." );
  }
}