Upload a File via FTP using Private Key File in C#

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();


                }
            }