Sftp provides a number of methods allowing you to asynchronously connect, login, upload, download, etc. Their names always end with Async. This means the method will begin some operation on a new thread and immediately return to the caller. When the operation has completed, the corresponding event will be raised notifying you that the operation has completed and in the event handler method you can check for the error and use the result, if provided.

The example following demonstrates how to connect to an SFTP server and download a file asynchronously:

Task-based approach

using System;
using System.IO;
using ComponentPro.IO;
using ComponentPro.Net;
using ComponentPro;

...

// Create a new class instance.
Sftp client = new Sftp();

// Connect to the SFTP server.
client.Connect("localhost");

// Authenticate.
client.Authenticate("test", "test");

// ... 
 
// Download remote file '/test.dat' to 'c:\test.dat' 
long transferred = await client.DownloadFileAsync("/test.dat", "c:\\test.dat");

// ...

Console.WriteLine("Bytes transferred: " + transferred);

// Disconnect.
client.Disconnect();

Imports System.IO
Imports ComponentPro.IO
Imports ComponentPro.Net
Imports ComponentPro

...

' Create a new class instance. 
Dim client As New Sftp()

' Connect to the SFTP server.
client.Connect("localhost")

' Authenticate.
client.Authenticate("test", "test")

' ... 
 
' Download remote file '/test.dat' to 'c:\test.dat' 
Dim transferred As Long = Await client.DownloadFileAsync("/test.dat", "c:\test.dat")

' ...

Console.WriteLine("Bytes transferred: " & transferred)

' Disconnect.
client.Disconnect()

Event-based approach

using System;
using System.IO;
using ComponentPro.IO;
using ComponentPro.Net;
using ComponentPro;

...

static void Main()
{
    // Create a new class instance. 
    Sftp client = new Sftp();

    // Connect to the SFTP server. 
    client.Connect("localhost");

    // Authenticate. 
    client.Authenticate("test", "test");

    // ... 
 
    // Register an event handler. 
    client.DownloadFileCompleted += client_DownloadFileCompleted;

    // Download remote file '/test.dat' to 'c:\test.dat' 
    client.DownloadFileAsync("/test.dat", "c:\\test.dat");

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

static void client_DownloadFileCompleted(object sender, ExtendedAsyncCompletedEventArgs<long> e)
{
    // Sftp client = (Sftp)sender; 
    if (e.Error != null)
        Console.WriteLine("Error: " + e.Error.Message);
    else 
    {
        long transferred = e.Result;
        Console.WriteLine("Bytes transferred: " + transferred);
    }
}

Imports System.IO
Imports ComponentPro.IO
Imports ComponentPro.Net
Imports ComponentPro

...

Shared Sub Main()
    ' Create a new class instance. 
    Dim client As New Sftp()

    ' Connect to the SFTP server. 
    client.Connect("localhost")

    ' Authenticate. 
    client.Authenticate("test", "test")

    ' ... 
 
    ' Register an event handler. 
    AddHandler client.DownloadFileCompleted, AddressOf client_DownloadFileCompleted

    ' Download remote file '/test.dat' to 'c:\test.dat' 
    client.DownloadFileAsync("/test.dat", "c:\test.dat")

    ' ... 
 
    ' Disconnect. 
    client.Disconnect()
End Sub 
 
Private Shared Sub client_DownloadFileCompleted(ByVal sender As Object, ByVal e As ExtendedAsyncCompletedEventArgs(Of Long))
    ' Sftp client = (Sftp)sender; 
    If e.Error IsNot Nothing Then 
        Console.WriteLine("Error: " & e.Error.Message)
    Else 
        Dim transferred As Long = e.Result
        Console.WriteLine("Bytes transferred: " & transferred)
    End If 
End Sub