Use DownloadMailMessageAsync methods to asynchronously download a message from the server. These methods asynchronously download a message from the server with execution occurring on a new thread, therefore they allow your next line of code to execute immediately.

In Task-based Asynchronous programs, the single asynchronous method represents the initiation and completion of an asynchronous operation. You may create the continuation code either explicitly, through methods on the Task class (for example, ContinueWith) or implicitly, by using language support built on top of continuations (for example, await in C#, Await in Visual Basic).

In Event-based Asynchronous programs, the event DownloadMailMessageCompleted is raised when the DownloadMailMessageAsync completes. In the event handler method of the DownloadMailMessageCompleted, you can check if there were any errors by using the Error property of the event data object.

The following example demonstrates how to asynchronously download a message from the server:

Task-based approach

using System;
using ComponentPro;
using ComponentPro.Net.Mail;

...

// Create a new instance of the Imap class.
Imap client = new Imap();

// Connect to the server.
client.Connect("myserver");

// Or you can specify the IMAP port with 
// client.Connect("myserver", 143); 
 
// Login to the server.
client.Authenticate("user", "password");

// ... 
 
// Select 'INBOX' mailbox.
client.Select("INBOX");

// Download a mail message with sequence number 1.
MailMessage msg = await client.DownloadMailMessageAsync(1);

// ...

Console.WriteLine("Message downloaded successfully.");
Console.WriteLine("Message ID: {0}, Subject: {1}", msg.MessageIdentifier, msg.Subject);

// Disconnect.
client.Disconnect();

Imports ComponentPro
Imports ComponentPro.Net.Mail

...

' Create a new instance of the Imap class. 
Dim client As New Imap()

' Connect to the server.
client.Connect("myserver")

' Or you can specify the IMAP port with 
' client.Connect("myserver", 143); 
 
' Login to the server.
client.Authenticate("user", "password")

' ... 
 
' Select 'INBOX' mailbox.
client.Select("INBOX")

' Download a mail message with sequence number 1. 
Dim msg As MailMessage = Await client.DownloadMailMessageAsync(1)

' ...

Console.WriteLine("Message downloaded successfully.")
Console.WriteLine("Message ID: {0}, Subject: {1}", msg.MessageIdentifier, msg.Subject)

' Disconnect.
client.Disconnect()

Event-based approach

using System;
using ComponentPro;
using ComponentPro.Net.Mail;

...

public void DoDownloadMailMessageAsync()
{
    // Create a new instance of the Imap class. 
    Imap client = new Imap();

    // Connect to the server. 
    client.Connect("myserver");

    // Or you can specify the IMAP port with 
    // client.Connect("myserver", 143); 
 
    // Login to the server. 
    client.Authenticate("user", "password");

    // ... 
 
    // Register an event handler. 
    client.DownloadMailMessageCompleted += client_DownloadMailMessageCompleted;

    // Select 'INBOX' mailbox. 
    client.Select("INBOX");

    // Download a mail message with sequence number 1. 
    client.DownloadMailMessageAsync(1);

    // ... 
 
    // Disconnect. 
    client.Disconnect();
}

void client_DownloadMailMessageCompleted(object sender, ExtendedAsyncCompletedEventArgs<MailMessage> e)
{
    if (e.Error != null)
    {
        Console.WriteLine("Error: " + e.Error.ToString());
    }
    else 
    {
        Console.WriteLine("Message downloaded successfully.");
        Console.WriteLine("Message ID: {0}, Subject: {1}", e.Result.MessageIdentifier, e.Result.Subject);
    }
}

Imports ComponentPro
Imports ComponentPro.Net.Mail

...

Public Sub DoDownloadMailMessageAsync()
    ' Create a new instance of the Imap class. 
    Dim client As New Imap()

    ' Connect to the server. 
    client.Connect("myserver")

    ' Or you can specify the IMAP port with 
    ' client.Connect("myserver", 143); 
 
    ' Login to the server. 
    client.Authenticate("user", "password")

    ' ... 
 
    ' Register an event handler. 
    AddHandler client.DownloadMailMessageCompleted, AddressOf client_DownloadMailMessageCompleted

    ' Select 'INBOX' mailbox. 
    client.Select("INBOX")

    ' Download a mail message with sequence number 1. 
    client.DownloadMailMessageAsync(1)

    ' ... 
 
    ' Disconnect. 
    client.Disconnect()
End Sub 
 
Private Sub client_DownloadMailMessageCompleted(ByVal sender As Object, ByVal e As ExtendedAsyncCompletedEventArgs(Of MailMessage))
    If e.Error IsNot Nothing Then 
        Console.WriteLine("Error: " & e.Error.ToString())
    Else 
        Console.WriteLine("Message downloaded successfully.")
        Console.WriteLine("Message ID: {0}, Subject: {1}", e.Result.MessageIdentifier, e.Result.Subject)
    End If 
End Sub