FTPS (FTP over SSL) in C#

I need some guidance. I need to develop a customizable FTP in C# that should be configured using App.Config file. Also, the FTP should push the data to any server from any client again depends on config file.

I will appreciate if someone can guide, if there is any API or any other useful suggestion, or move me in the right direction.

You can use FtpWebRequest; however, this is fairly low level. There is a higher-level class WebClient, which requires much less code for many scenarios; however, it doesn't support FTP/SSL by default. Fortunately, you can make WebClient work with FTP/SSL by registering your own prefix:

private void RegisterFtps()
{
    WebRequest.RegisterPrefix("ftps", new FtpsWebRequestCreator());
}

private sealed class FtpsWebRequestCreator : IWebRequestCreate
{
    public WebRequest Create(Uri uri)
    {
        FtpWebRequest webRequest = (FtpWebRequest)WebRequest.Create(uri.AbsoluteUri.Remove(3, 1)); // Removes the "s" in "ftps://".
        webRequest.EnableSsl = true;
        return webRequest;
    }
}

Once you do this, you can use WebClient almost like normal, except that your URIs start with "ftps://" instead of "ftp://". The one caveat is that you have to specify the method parameter, since there won't be a default one. E.g.

using (var webClient = new WebClient()) {
    // Note here that the second parameter can't be null.
    webClient.UploadFileAsync(uploadUri, WebRequestMethods.Ftp.UploadFile, fileName, state);
}

The accepted answer works, indeed. But I find it too cumbersome to register a prefix, implement an interface, and all that stuff, particularly, if you need it just for one transfer.

FtpWebRequest is not that difficult to use. So I believe that for one-time use, it's better to go this way:

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.EnableSsl = true;
request.Method = WebRequestMethods.Ftp.UploadFile;  

using (Stream fileStream = File.OpenRead(@"C:\local\path\file.zip"))
using (Stream ftpStream = request.GetRequestStream())
{
    fileStream.CopyTo(ftpStream);
}

The key is the EnableSsl property.

For other scenarios, see:
Upload and download a binary file to/from FTP server in C#/.NET