要使用C# FluentFTP庫上傳文件，首先確保已經安裝了FluentFTP NuGet包。然后，按照以下步驟操作：

1. 引入必要的命名空間：

using System;
using System.IO;
using FluentFTP;

2. 創建一個FtpClient對象并連接到FTP服務器：

string host = "your_ftp_host";
int port = 21; // 默認的FTP端口是21
string username = "your_username";
string password = "your_password";

FtpClient client = new FtpClient(host, port, username, password);
client.EncryptionMode = FtpEncryptionMode.Explicit; // 設置加密模式為顯式
client.Connect();

3. 檢查連接是否成功：

if (!client.IsConnected)
{
    Console.WriteLine("Failed to connect to FTP server.");
    return;
}

4. 使用UploadFile方法上傳文件：

string localFilePath = @"C:\path\to\your\local\file.txt"; // 本地文件路徑
string remoteFilePath = "/remote/path/file.txt"; // FTP服務器上的目標路徑

bool success = client.UploadFile(localFilePath, remoteFilePath);

if (success)
{
    Console.WriteLine("File uploaded successfully.");
}
else
{
    Console.WriteLine("Failed to upload file.");
}

5. 斷開與FTP服務器的連接：

client.Disconnect();

完整的示例代碼如下：

using System;
using System.IO;
using FluentFTP;

namespace FtpUploadExample
{
    class Program
    {
        static void Main(string[] args)
        {
            string host = "your_ftp_host";
            int port = 21;
            string username = "your_username";
            string password = "your_password";

            FtpClient client = new FtpClient(host, port, username, password);
            client.EncryptionMode = FtpEncryptionMode.Explicit;
            client.Connect();

            if (!client.IsConnected)
            {
                Console.WriteLine("Failed to connect to FTP server.");
                return;
            }

            string localFilePath = @"C:\path\to\your\local\file.txt";
            string remoteFilePath = "/remote/path/file.txt";

            bool success = client.UploadFile(localFilePath, remoteFilePath);

            if (success)
            {
                Console.WriteLine("File uploaded successfully.");
            }
            else
            {
                Console.WriteLine("Failed to upload file.");
            }

            client.Disconnect();
        }
    }
}

請根據實際情況替換your_ftp_host、your_username、your_password和本地文件路徑。運行此代碼后，文件將從本地上傳到FTP服務器。