Application to download all files from a directory in remote FTP

I'm trying to make an installer-type application for a proprietary system.

The process it does is: it creates a directory and two subdirectories on a PC that will use the system.

After creating the directory and subdirectories, the application accesses ftp and downloads the executables that are in the ftp to the subdirectories that are in the machine.

The code I'm using is as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Security.AccessControl;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace App_Install_Golden_Premium
{
    public partial class frmInstala : Form
    {
        public frmInstala()
        {
            InitializeComponent();
        }

        private void btInstalar_Click(object sender, EventArgs e)
        {
            string diretorio = @"C:\Program Files\Teste\";
            string subdiretorio;
            string diretorioFTP = string.Empty;
            string usuario;
            string senha;
            string arquivo = string.Empty;
            var pathWithEnv = @"%USERPROFILE%\Área de Trabalho";
            var filePath = Environment.ExpandEnvironmentVariables(pathWithEnv);
            string dirDesktop = filePath;
            progressBar1.Value = 0;


            // Pega dominio/usuario logado atual
            string informacao = System.Security.Principal.WindowsIdentity.GetCurrent().Name; ;

            if (rbGolden.Checked)
            {
                subdiretorio = "Golden";
                diretorioFTP = "ftp://ftp.ftp remoto";
                usuario = "usuario";
                senha = "senha";
            }
            else
            {
                subdiretorio = "Premium";
                diretorioFTP = "ftp://ftp.ftp remoto";
                usuario = "usuario";
                senha = "senha";
            }

            diretorio += subdiretorio;

            if (Directory.Exists(diretorio))
            {
                if (MessageBox.Show("O Diretório já existe!\n- Se deseja SAIR, Clique em [CANCELAR]\n- Se deseja CONTINUAR, Clique em [REPETIR] ", "Criação de Diretorio", MessageBoxButtons.RetryCancel, MessageBoxIcon.Hand) == DialogResult.Cancel)
                {
                    Application.Exit();
                }
            }
            else
            {
                Directory.CreateDirectory(diretorio);

                DirectorySecurity regras = new DirectorySecurity();
                regras.AddAccessRule(new FileSystemAccessRule(informacao, FileSystemRights.FullControl, AccessControlType.Allow));

                MessageBox.Show("Diretório Criado com Sucesso!", "Criação de Diretório", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(diretorioFTP);
            request.Method = WebRequestMethods.Ftp.DownloadFile;
            request.Credentials = new NetworkCredential(usuario, senha);
            FtpWebResponse response = (FtpWebResponse)request.GetResponse();

            DirectoryInfo di = new DirectoryInfo(diretorioFTP);

            progressBar1.Maximum = di.GetFiles().Length;

            foreach( var item in di.GetFiles())
            {
                arquivo = Path.Combine(diretorio, item.Name);
                File.Copy(item.FullName, arquivo);
                lblStatus.Refresh();
                progressBar1.Value++;
            }
            MessageBox.Show("Instalação efetuada com sucesso!", "Aviso",
            MessageBoxButtons.OK, MessageBoxIcon.Information);
            lblStatus.Visible = false;
            progressBar1.Maximum = 0;
        }
    }
}

Being shown error on this line

DirectoryInfo di = new DirectoryInfo(diretorioFTP);

And the error in question is this:

System.NotSupportedException não foi manipulada
HResult=-2146233067
Message=Não há suporte para o formato do caminho dado.
Source=mscorlib
StackTrace: em System.Security.Permissions.FileIOPermission.EmulateFileIOPermissionChecks(String fullPath)
   em System.IO.DirectoryInfo.Init(String path, Boolean checkHost)
   em System.IO.DirectoryInfo..ctor(String path)
   em App_Install_Golden_Premium.frmInstala.btInstalar_Click(Object sender, EventArgs e) na D:\Fabio\Visual Studio\Projeto Golden Premium Download e instalacao\Instalador_golden_premium\App_Install_Golden_Premium\App_Install_Golden_Premium\frmInstala.cs:linha 78
   em System.Windows.Forms.Control.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   em System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   em System.Windows.Forms.Control.WndProc(Message& m)
   em System.Windows.Forms.ButtonBase.WndProc(Message& m)
   em System.Windows.Forms.Button.WndProc(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   em System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   em System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   em System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.Run(Form mainForm)
   em App_Install_Golden_Premium.Program.Main() na D:\Fabio\Visual Studio\Projeto Golden Premium Download e instalacao\Instalador_golden_premium\App_Install_Golden_Premium\App_Install_Golden_Premium\Program.cs:linha 19
   em System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   em System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   em Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   em System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   em System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   em System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   em System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   em System.Threading.ThreadHelper.ThreadStart()
InnerException: