Upload File via FTP using Private Key File

To easy up the work, I'm using SSH.NET Library to assist with the uploading process. Before start using the private key file you must convert it to a supported format by SSH.NET. For that, I'm using PuTTygen.

<appSettings>
    <add key="FTPUploadPath" value="/mypath/ftpUploadPath"/>
    <add key="FTPDownloadPath" value="/mypath/localpath"/>
    <add key="FTPHost" value="host"/>
    <add key="FTPPort" value="port"/>
    <add key="FTPUserName" value="userName"/>
    <add key="FTPPass" value="Password"/>
    <!--private key file must be converted into a valid format using PuTTygen-->
    <add key="PrivateKeyFile" value="\\mypath\WinSCP\SFX_PuTTygen.ppk"/>        
  </appSettings>

public static void FtpUploadFileUsingPrivateKeyFile(string ftpUploadPath, string localPath, string host, int port, string userName, string password)
  {
                var keyFile = new PrivateKeyFile(@ConfigHelper.PrivateKeyFile, password);
                var keyFiles = new[] { keyFile };
                
                var methods = new List<AuthenticationMethod>();
                methods.Add(new PasswordAuthenticationMethod(userName, password));
                methods.Add(new PrivateKeyAuthenticationMethod(userName, keyFiles));

                var con = new ConnectionInfo(host, port, userName, methods.ToArray());
                using (var client = new SftpClient(con))
                {
                    client.Connect();

                    FileInfo f = new FileInfo(localPath);
                    string uploadfile = f.FullName;

                    if (client.IsConnected)
                    {
                        Console.WriteLine("Connected to FTP. Transferring File " + f.FullName);
                    }
                    var fileStream = new FileStream(uploadfile, FileMode.Open);
                    if (fileStream != null)
                    {
                        Console.WriteLine("YOU ARE NOT NULL");
                    }
                    client.BufferSize = 4 * 1024;
                    client.UploadFile(fileStream, ftpUploadPath + "/" + f.Name, null); //ConfigHelper.FTPUploadPath
                    client.Disconnect();
                    client.Dispose();


                }
            }