SFTP 非同期

using Renci.SshNet;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;

public class SftpManager : IDisposable
{
    private SftpClient sftpClient;

    public SftpManager(string host, int port, string username, string privateKeyFilePath, string passphrase = null)
    {
        var privateKeyFile = new PrivateKeyFile(privateKeyFilePath, passphrase);
        var keyFiles = new[] { privateKeyFile };

        var connectionInfo = new ConnectionInfo(host, port, username, keyFiles);

        sftpClient = new SftpClient(connectionInfo);
    }

    public async Task ConnectAsync()
    {
        if (!sftpClient.IsConnected)
            await Task.Run(() => sftpClient.ConnectAsync());
    }

    public async Task DisconnectAsync()
    {
        if (sftpClient.IsConnected)
            await Task.Run(() => sftpClient.Disconnect());
    }

    public async Task UploadFileAsync(string localFilePath, string remoteFilePath)
    {
        try
        {
            using (var fileStream = new FileStream(localFilePath, FileMode.Open))
            {
                await Task.Run(() => sftpClient.UploadFile(fileStream, remoteFilePath));
            }
        }
        catch (Exception ex)
        {
            HandleSftpException(ex);
        }
    }

    public async Task DownloadFileAsync(string remoteFilePath, string localFilePath)
    {
        try
        {
            using (var fileStream = File.OpenWrite(localFilePath))
            {
                await Task.Run(() => sftpClient.DownloadFile(remoteFilePath, fileStream));
            }
        }
        catch (Exception ex)
        {
            HandleSftpException(ex);
        }
    }

    public async Task DeleteFileAsync(string remoteFilePath)
    {
        try
        {
            await Task.Run(() => sftpClient.DeleteFile(remoteFilePath));
        }
        catch (Exception ex)
        {
            HandleSftpException(ex);
        }
    }

    // 他のメソッドも同様に非同期メソッドに変更

    public async Task<bool> IsConnectedAsync()
    {
        return await Task.Run(() => sftpClient.IsConnected);
    }

    private void HandleSftpException(Exception ex)
    {
        Console.WriteLine($"SFTP Error: {ex.Message}");
    }

    public void Dispose()
    {
        if (sftpClient != null)
        {
            sftpClient.Dispose();
            sftpClient = null;
        }
    }
}