Retrieve filename and ID with Google Drive API in C#

Question

I am trying to retrieve filename and ID list with Google Drive API (the latest Drive API version v3 is used here) as a first step in order to analyze and manipulate these files on Google Drive. The experimental implementation is as below. (Note: credentials.json file is needed and the step to generate this file is here. )

The experimental implementation

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.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace GoogleDriveFileManager
{
 class Program
 {
 static string[] Scopes = { DriveService.Scope.DriveReadonly };
 static string ApplicationName = "GoogleDriveFileManager";
 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($"Credential file saved to: {credPath}");
 }
 // Create Drive API service.
 var service = new DriveService(new BaseClientService.Initializer()
 {
 HttpClientInitializer = credential,
 ApplicationName = ApplicationName,
 });
 // Define parameters of request.
 FilesResource.ListRequest listRequest = service.Files.List();
 listRequest.PageSize = 1000;
 listRequest.Fields = "nextPageToken, files(id, name)";
 // List files.
 IList<Google.Apis.Drive.v3.Data.File> files = listRequest.Execute()
 .Files;
 Console.WriteLine("Files:");
 Console.WriteLine($"file.Name{new String('\t', 6)}file.Id{new String('\t', 8)}file.ModifiedTime");
 if (files != null && files.Count > 0)
 {
 foreach (var file in files)
 {
 Console.WriteLine(
 $"{file.Name.PadRight(56)}{file.Id.PadRight(36)}{file.ModifiedTime}"
 );
 }
 }
 else
 {
 Console.WriteLine("No files found.");
 }
 Console.Read();
 }
 }
}

If there is any possible improvement about potential drawback or unnecessary overhead, please let me know.

• Peter Csala: Which version of C# are you using? I'm asking it because for instance since C# 7.1 async main is supported.

Answer 1

First of all let me clarify that I'm not familiar with the Google Drive API. I've done some refactoring but I haven't tested it (just make it compile).

If I can assume you are using greater C# version than 8 then you can refactor your code like this:

using static {YourMainNamespace}.Constants;
class Program
{
 static async Task Main(string[] args)
 {
 UserCredential credential = await AuthorizeAgainstGoogleDriveAsync();
 IList<Google.Apis.Drive.v3.Data.File> files = await GetFilesMetaInfoAsync(credential);
 DisplayFilesMetaInfoInTabularFashion(files);
 Console.ReadLine();
 }
 static async Task<UserCredential> AuthorizeAgainstGoogleDriveAsync(
 string sourceRelativePath = Authorize.RelativeFilePath.Source,
 string targetRelativePath = Authorize.RelativeFilePath.Target)
 {
 using var stream = new FileStream(sourceRelativePath, FileMode.Open, FileAccess.Read);
 var credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
 GoogleClientSecrets.Load(stream).Secrets,
 Authorize.Scopes,
 Authorize.User,
 CancellationToken.None,
 new FileDataStore(targetRelativePath, true));
 Console.WriteLine($"Credential file saved to: {Authorize.RelativeFilePath.Target}");
 return credential;
 }
 static async Task<IList<Google.Apis.Drive.v3.Data.File>> GetFilesMetaInfoAsync(
 UserCredential credential,
 string applicationName = GetFiles.ApplicationName,
 int pageSize = GetFiles.PageSize,
 string fields = GetFiles.Fields)
 {
 var service = new DriveService(new BaseClientService.Initializer()
 {
 HttpClientInitializer = credential,
 ApplicationName = applicationName,
 });
 FilesResource.ListRequest listRequest = service.Files.List();
 listRequest.PageSize = pageSize;
 listRequest.Fields = fields;
 var fileList = await listRequest.ExecuteAsync();
 return fileList.Files;
 }
 static void DisplayFilesMetaInfoInTabularFashion(IList<Google.Apis.Drive.v3.Data.File> files)
 {
 Console.WriteLine("Files:");
 Console.WriteLine($"{DisplayFiles.Name}{new string('\t', 6)}{DisplayFiles.Id}{new string('\t', 8)}{DisplayFiles.ModifiedTime}");
 if (files == null || files.Count <= 0)
 {
 Console.WriteLine(DisplayFiles.NoFileMessage);
 return;
 }
 foreach (var file in files)
 {
 Console.WriteLine($"{file.Name,-56}{file.Id,-36}{file.ModifiedTime}");
 }
 
 }
}
static class Constans
{
 public static class Authorize
 {
 public const string User = "user";
 public readonly static string[] Scopes = new[] { DriveService.Scope.DriveReadonly };
 public static class RelativeFilePath
 {
 public const string Source = "credentials.json";
 public const string Target = "token.json";
 }
 }
 public static class GetFiles
 {
 public const string ApplicationName = "GoogleDriveFileManager";
 public const int PageSize = 1000;
 public const string Fields = "nextPageToken, files(id, name)";
 }
 public static class DisplayFiles
 {
 private const string prefix = "file.";
 public const string Name = prefix + nameof(Name);
 public const string Id = prefix + nameof(Id);
 public const string ModifiedTime = prefix + nameof(ModifiedTime);
 public const string NoFileMessage = "No files found.";
 }
}

---

Let me give you some context for each part:

Main

static async Task Main(string[] args)
{
 UserCredential credential = await AuthorizeAgainstGoogleDriveAsync();
 IList<Google.Apis.Drive.v3.Data.File> files = await GetFilesMetaInfoAsync(credential);
 DisplayFilesMetaInfoInTabularFashion(files);
 Console.ReadLine();
}

• I've made your Main async (supported since C# 7.1) to be able to use async-await
• I've split your logic into three smaller functions to make your Main short and concise
  • If the scope of the application is this small then you can use shorter names of course, like
    • AuthorizeAsync
    • GetFiles
    • DisplayFiles

Constants

using static {YourMainNamespace}.Constants;
...
static class Constans
{
 public static class Authorize
 {
 public const string User = "user";
 public readonly static ImmutableArray<string> Scopes = new[] { DriveService.Scope.DriveReadonly }.ToImmutableArray();
 public static class RelativeFilePath
 {
 public const string Source = "credentials.json";
 public const string Target = "token.json";
 }
 }
 public static class GetFiles
 {
 public const string ApplicationName = "GoogleDriveFileManager";
 public const int PageSize = 1000;
 public const string Fields = "nextPageToken, files(id, name)";
 }
 public static class DisplayFiles
 {
 private const string prefix = "file.";
 public const string Name = prefix + nameof(Name);
 public const string Id = prefix + nameof(Id);
 public const string ModifiedTime = prefix + nameof(ModifiedTime);
 public const string NoFileMessage = "No files found.";
 }
}

• I've put all of the hardcoded values into a hierarchical structure
  • Because I'm unfamiliar with the domain I've organize them based on the usage
  • In normal cases you should organize them based on their semantics
• I've used const (which is implicit static) to prevent modification
• In case of Scope I've used ImmutableArray to prevent modification
  • Here I can't use const but it could (and should) be marked as readonly
• I've used using static to avoid prefixing with Constants each and every time

AuthorizeAgainstGoogleDriveAsync

static async Task<UserCredential> AuthorizeAgainstGoogleDriveAsync(
 string sourceRelativePath = Authorize.RelativeFilePath.Source,
 string targetRelativePath = Authorize.RelativeFilePath.Target)
{
 using var stream = new FileStream(sourceRelativePath, FileMode.Open, FileAccess.Read);
 var credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
 GoogleClientSecrets.Load(stream).Secrets,
 Authorize.Scopes,
 Authorize.User,
 CancellationToken.None,
 new FileDataStore(targetRelativePath, true));
 Console.WriteLine($"Credential file saved to: {Authorize.RelativeFilePath.Target}");
 return credential;
}

• I've made the source and target file paths configurable (but with default values)
  • If you wish you can make the same with user and scopes
• One can argue whether the Console.WriteLine should belong here or inside the Main
  • I've put it here to make the main as concise as possible
  • But from reusability point of view it should not belong here
• I've used using declaration (which is a C# 8 feature) to avoid the block operator ({ ... })

GetFilesMetaInfoAsync

static async Task<IList<Google.Apis.Drive.v3.Data.File>> GetFilesMetaInfoAsync(
 UserCredential credential,
 string applicationName = GetFiles.ApplicationName,
 int pageSize = GetFiles.PageSize,
 string fields = GetFiles.Fields)
{
 var service = new DriveService(new BaseClientService.Initializer()
 {
 HttpClientInitializer = credential,
 ApplicationName = applicationName,
 });
 FilesResource.ListRequest listRequest = service.Files.List();
 listRequest.PageSize = pageSize;
 listRequest.Fields = fields;
 var fileList = await listRequest.ExecuteAsync();
 return fileList.Files;
}

• I've made this API call to async (Execute >> ExecuteAsync) to make use of the async non-blocking I/O
• I've declared the function with three optional parameters to be able to customize the request if needed
• I've realized that you are not making use of the nextPageToken but I did not remove it
  • I've assumed that the implementation of paging will be your next step

DisplayFilesMetaInfoInTabularFashion

static void DisplayFilesMetaInfoInTabularFashion(IList<Google.Apis.Drive.v3.Data.File> files)
{
 Console.WriteLine("Files:");
 Console.WriteLine($"{DisplayFiles.Name}{new string('\t', 6)}{DisplayFiles.Id}{new string('\t', 8)}{DisplayFiles.ModifiedTime}");
 if (files == null || files.Count <= 0)
 {
 Console.WriteLine(DisplayFiles.NoFileMessage);
 return;
 }
 foreach (var file in files)
 {
 Console.WriteLine($"{file.Name,-56}{file.Id,-36}{file.ModifiedTime}");
 } 
}

• This operation is tightly coupled to the request
  • It highly relies on the retrieved fields
  • So, it might make sense to it make more dynamic if needed
• I've used new string instead of new String
  • I suggest to read this article
• I've reverted the if statement to use the early exit pattern
  • With this the main logic (foreach) is not indented
• I've also used the capabilities of string interpolation to avoid calls like PadRight