1、引用CoreFtp的方法

1）下载代码引用

下载地址：https://github.com/sparkeh9/CoreFTP/releases

2）使用Nuget引用

在Nuget管理程序中，搜索'CoreFtp' =》选中然后点击'安装'。

相关文档：VS(Visual Studio)中Nuget的使用

2、连接FTP/S server

using ( var ftpClient = new FtpClient( new FtpClientConfiguration
                                             {
                                                 Host = "localhost",
                                                 Username = "user",
                                                 Password = "password",
                                                 Port = 990,
                                                 EncryptionType = FtpEncryption.Implicit,
                                                 IgnoreCertificateErrors = true
                                             } ) )
{
    await ftpClient.LoginAsync();
}

3、从FTP/S server下载文件到本地

using ( var ftpClient = new FtpClient( new FtpClientConfiguration
                                             {
                                                 Host = "localhost",
                                                 Username = "user",
                                                 Password = "password"
                                             } ) )
{
	var tempFile = new FileInfo( "C:\\test.png" );
    await ftpClient.LoginAsync();
    using ( var ftpReadStream = await ftpClient.OpenFileReadStreamAsync( "test.png" ) )
    {
        using ( var fileWriteStream = tempFile.OpenWrite() )
        {
            await ftpReadStream.CopyToAsync( fileWriteStream );
        }
    }
} 

4、上传文件到FTP Server 

using ( var ftpClient = new FtpClient( new FtpClientConfiguration
                                    {
                                        Host = "localhost",
                                        Username = "user",
                                        Password = "password"
                                    } ) )
{
	var fileinfo = new FileInfo( "C:\\test.png" );
    await ftpClient.LoginAsync();    
    using ( var writeStream = await ftpClient.OpenFileWriteStreamAsync( "test.png" ) )
    {
        var fileReadStream = fileinfo.OpenRead();
        await fileReadStream.CopyToAsync( writeStream );
    }
} 

5、改变FTP Server当前目录、创建目录、删除文件，删除目录 

using (var ftpClient = new FtpClient(new FtpClientConfiguration
           {
               Host = "localhost",
               Username = "user",
               Password = "password"            }))
           {
               var fileinfo = new FileInfo("C:\\test.png");
               await ftpClient.LoginAsync();
               //改变目录
               await ftpClient.ChangeWorkingDirectoryAsync("work");
               //创建目录
               await ftpClient.CreateDirectoryAsync("abc");
               //删除目录
               await ftpClient.DeleteDirectoryAsync("abc");
               //删除文件
               await ftpClient.DeleteFileAsync("test.png");
           }

官方文档：https://github.com/sparkeh9/CoreFTP