CertificateReceived Event

public event EventHandler<TEventArgs> CertificateReceived

Public Event CertificateReceived EventHandler(Of TEventArgs)

public:
 event EventHandler<TEventArgs>^ CertificateReceived

Show how to handle the CertificateReceived event.

using System;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using ComponentPro.Net;
using ComponentPro.Net.Mail;
using ComponentPro.Security.Certificates;

...

public void HandleCertificateReceivedEvent()
{
    // Create a new instance. 
    Pop3 client = new Pop3();

    client.CertificateReceived += client_CertificateReceived;

    // Connect to the POP3 server. 
    client.Connect("myserver", 110, SslSecurityMode.Explicit);

    // Authenticate. 
    client.Authenticate("userName", "password");

    // Do something here... 
    // ... 
    

    // Disconnect. 
    client.Disconnect();
}

/// <summary> 
/// Returns all issues of the given certificate. 
/// </summary> 
/// <param name="status">The certificate verification result.</param> 
/// <param name="code">The error code.</param> 
/// <returns>Certificate problems.</returns> 
private static string GetCertProblem(CertificateVerificationStatus status, int code)
{
    switch (status)
    {
        case CertificateVerificationStatus.TimeNotValid:
            return "Server's certificate has expired or is not valid yet.";

        case CertificateVerificationStatus.Revoked:
            return "Server's certificate has been revoked.";

        case CertificateVerificationStatus.UnknownCa:
            return "Server's certificate was issued by an unknown authority.";

        case CertificateVerificationStatus.UntrustedRoot:
            return "Server's certificate was issued by an untrusted authority.";

        case CertificateVerificationStatus.IncompleteChain:
            return "Server's certificate does not chain up to a trusted root authority.";

        case CertificateVerificationStatus.Malformed:
            return "Server's certificate is malformed.";

        case CertificateVerificationStatus.CnNotMatch:
            return "Server hostname does not match the certificate.";

        case CertificateVerificationStatus.UnknownError:
            return string.Format("Error {0:x} encountered while validating server's certificate.", code);

        default:
            return status.ToString();
    }
}

void client_CertificateReceived(object sender, ComponentPro.Security.CertificateReceivedEventArgs e)
{
    X509Certificate2 cert = e.ServerCertificates[0];

    CertificateVerificationStatus status = e.Status;

    CertificateVerificationStatus[] values = (CertificateVerificationStatus[])Enum.GetValues(typeof(CertificateVerificationStatus));

    StringBuilder sbIssues = new StringBuilder();
    for (int i = 0; i < values.Length; i++)
    {
        // Matches the validation status? 
        if ((status & values[i]) == 0)
            continue;

        // The issue is processed. 
        status ^= values[i];

        sbIssues.AppendFormat("{0}\r\n", GetCertProblem(values[i], e.ErrorCode));
    }

    Console.WriteLine("Issue: " + sbIssues.ToString());

    Console.WriteLine("Subject: " + cert.SubjectName.Name);
    Console.WriteLine("Issuer: " + cert.IssuerName.Name);
    Console.WriteLine("Effective Date: " + cert.NotBefore);
    Console.WriteLine("Expiry Date: " + cert.NotAfter);
    Console.ResetColor();
    Console.Write("Do you want to accept this certificate (Add to trusted list, Yes, No) [a,y,n]?");

    string response = Console.ReadLine().Trim().ToLower();

    // Add certiticate of the issuer CA to the trusted list. 
    if (response == "a")
    {
        e.AddToTrustedRoot = true;
    }
    else if (response == "y")
    {
        e.Accept = true;
    }
}

Imports System.Security.Cryptography.X509Certificates
Imports System.Text
Imports ComponentPro.Net
Imports ComponentPro.Net.Mail
Imports ComponentPro.Security.Certificates

...

Public Sub HandleCertificateReceivedEvent()
    ' Create a new instance. 
    Dim client As New Pop3()

    AddHandler client.CertificateReceived, AddressOf client_CertificateReceived

    ' Connect to the POP3 server. 
    client.Connect("myserver", 110, SslSecurityMode.Explicit)

    ' Authenticate. 
    client.Authenticate("userName", "password")

    ' Do something here... 
    ' ...


    ' Disconnect. 
    client.Disconnect()
End Sub 
 
''' <summary> 
''' Returns all issues of the given certificate. 
''' </summary> 
''' <param name="status">The certificate verification result.</param> 
''' <param name="code">The error code.</param> 
''' <returns>Certificate problems.</returns> 
Private Shared Function GetCertProblem(ByVal status As CertificateVerificationStatus, ByVal code As Integer) As String 
    Select Case status
        Case CertificateVerificationStatus.TimeNotValid
            Return "Server's certificate has expired or is not valid yet." 
 
        Case CertificateVerificationStatus.Revoked
            Return "Server's certificate has been revoked." 
 
        Case CertificateVerificationStatus.UnknownCa
            Return "Server's certificate was issued by an unknown authority." 
 
        Case CertificateVerificationStatus.UntrustedRoot
            Return "Server's certificate was issued by an untrusted authority." 
 
        Case CertificateVerificationStatus.IncompleteChain
            Return "Server's certificate does not chain up to a trusted root authority." 
 
        Case CertificateVerificationStatus.Malformed
            Return "Server's certificate is malformed." 
 
        Case CertificateVerificationStatus.CnNotMatch
            Return "Server hostname does not match the certificate." 
 
        Case CertificateVerificationStatus.UnknownError
            Return String.Format("Error {0:x} encountered while validating server's certificate.", code)

        Case Else 
            Return status.ToString()
    End Select 
End Function 
 
Private Sub client_CertificateReceived(ByVal sender As Object, ByVal e As ComponentPro.Security.CertificateReceivedEventArgs)
    Dim cert As X509Certificate2 = e.ServerCertificates(0)

    Dim status As CertificateVerificationStatus = e.Status

    Dim values() As CertificateVerificationStatus = CType(System.Enum.GetValues(GetType(CertificateVerificationStatus)), CertificateVerificationStatus())

    Dim sbIssues As New StringBuilder()
    For i As Integer = 0 To values.Length - 1
        ' Matches the validation status? 
        If (status And values(i)) = 0 Then 
            Continue For 
        End If 
 
        ' The issue is processed. 
        status = status Xor values(i)

        sbIssues.AppendFormat("{0}" & vbCrLf, GetCertProblem(values(i), e.ErrorCode))
    Next i

    Console.WriteLine("Issue: " & sbIssues.ToString())

    Console.WriteLine("Subject: " & cert.SubjectName.Name)
    Console.WriteLine("Issuer: " & cert.IssuerName.Name)
    Console.WriteLine("Effective Date: " & cert.NotBefore)
    Console.WriteLine("Expiry Date: " & cert.NotAfter)
    Console.ResetColor()
    Console.Write("Do you want to accept this certificate (Add to trusted list, Yes, No) [a,y,n]?")

    Dim response As String = Console.ReadLine().Trim().ToLower()

    ' Add certiticate of the issuer CA to the trusted list. 
    If response = "a" Then 
        e.AddToTrustedRoot = True 
    ElseIf response = "y" Then 
        e.Accept = True 
    End If 
End Sub

Reference