更新或如果不存在创建文件Google Drive .NET API

using Google.Apis.Auth.OAuth2;
using Google.Apis.Drive.v3;
using Google.Apis.Drive.v3.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System;
using System.IO;
using System.Threading;

public class Program
{
    static string[] Scopes = { DriveService.Scope.Drive };
    static string ApplicationName = "Your Application Name";

    static void Main(string[] args)
    {
        UserCredential credential;

        using (var stream = new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
        {
            string credPath = "token.json";
            credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                GoogleClientSecrets.Load(stream).Secrets,
                Scopes,
                "user",
                CancellationToken.None,
                new FileDataStore(credPath, true)).Result;
            Console.WriteLine("Credential file saved to: " + credPath);
        }

        var service = new DriveService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = ApplicationName,
        });

        // 创建或更新文件
        string fileId = "your-file-id"; // 如果是更新文件，请提供文件的ID
        string filePath = "path-to-your-file"; // 文件的本地路径

        var fileMetadata = new File()
        {
            Name = "your-file-name",
        };

        FilesResource.CreateMediaUpload request;

        if (string.IsNullOrEmpty(fileId))
        {
            request = service.Files.Create(fileMetadata, new FileStream(filePath, FileMode.Open));
        }
        else
        {
            request = service.Files.Update(fileMetadata, fileId, new FileStream(filePath, FileMode.Open));
        }

        request.Fields = "id";
        request.Upload();

        var file = request.ResponseBody;
        Console.WriteLine("File ID: " + file.Id);
    }
}