.NET quickstart

Complete the steps described in the rest of this page to create a simple .NET console application that makes requests to the Google Tasks API.

Prerequisites

To run this quickstart, you need the following prerequisites:

  • Authorization credentials for a desktop application. To learn how to create credentials for a desktop application, refer to Create credentials.

  • A Google account with Google Tasks enabled.

Step 1: Prepare the project

  1. Create a new Visual C# Console Application project in Visual Studio.
  2. Open the NuGet Package Manager Console, select the package source nuget.org, and run the following command:
Install-Package Google.Apis.Tasks.v1

Step 2: Set up the sample

  1. Drag credentials.json, downloaded as a prerequisite, into your Visual Studio Solution Explorer.
  2. Select credentials.json, and then go to the Properties window and set the Copy to Output Directory field to Copy always.
  3. Replace the contents of Program.cs with the following code:

tasks/TasksQuickstart/TasksQuickstart.cs
using Google.Apis.Auth.OAuth2;
using Google.Apis.Tasks.v1;
using Google.Apis.Tasks.v1.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;

namespace TasksQuickstart
{
    // Class to demonstrate the use of Tasks list tasks API
    class Program
    {
        /* Global instance of the scopes required by this quickstart.
         If modifying these scopes, delete your previously saved token.json/ folder. */
        static string[] Scopes = { TasksService.Scope.TasksReadonly };
        static string ApplicationName = "Google Tasks API .NET Quickstart";

        static void Main(string[] args)
        {
            try
            {
                UserCredential credential;
                // Load client secrets.
                using (var stream =
                       new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
                {
                    /* The file token.json stores the user's access and refresh tokens, and is created
                     automatically when the authorization flow completes for the first time. */
                    string credPath = "token.json";
                    credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                        GoogleClientSecrets.FromStream(stream).Secrets,
                        Scopes,
                        "user",
                        CancellationToken.None,
                        new FileDataStore(credPath, true)).Result;
                    Console.WriteLine("Credential file saved to: " + credPath);
                }

                // Create Google Tasks API service.
                var service = new TasksService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = ApplicationName
                });

                // Define parameters of request.
                TasklistsResource.ListRequest listRequest = service.Tasklists.List();
                listRequest.MaxResults = 10;

                // List task lists.
                IList<TaskList> taskLists = listRequest.Execute().Items;
                Console.WriteLine("Task Lists:");
                if (taskLists == null || taskLists.Count == 0)
                {
                    Console.WriteLine("No task lists found.");
                    return;
                }
                foreach (var taskList in taskLists)
                {
                    Console.WriteLine("{0} ({1})", taskList.Title, taskList.Id);
                }
            }
            catch (FileNotFoundException e)
            {
                Console.WriteLine(e.Message);
            }
        }
    }
}

Step 3: Run the sample

Build and run the sample by clicking Start in the Visual Studio toolbar.

The first time you run the sample, it prompts you to authorize access:

  1. The sample attempts to open a new window or tab in your default browser. If this fails, copy the URL from the console and manually open it in your browser.

    If you're not already signed in to your Google account, you're prompted to sign in. If you're signed in to multiple Google accounts, you're asked to select one account to use for authorization.

  2. Click the Accept button.
  3. The sample proceeds automatically, and you may close the window/tab.

Notes

  • Authorization information is stored on the file system, so subsequent executions won't prompt for authorization.
  • The authorization flow in this example is designed for a command-line application. For information on how to perform authorization in a web application, see the web applications section of the library's OAuth 2.0 guide.

Troubleshooting

This section describes some common issues that you may encounter while attempting to run this quickstart and suggests possible solutions.

Could not load file or assembly 'Microsoft.Threading.Tasks'

This error can occur when using an outdated or incorrectly installed version of the Microsoft.Bcl.Async package. Reinstall the package using the following command in the NuGet Package Manager Console:

Update-Package Microsoft.Bcl.Async -reinstall

You are prompted to restart Visual Studio to complete the installation.

This app isn't verified

If the OAuth consent screen displays the warning "This app isn't verified," your app is requesting scopes that provide access to sensitive user data. If your application uses sensitive scopes, your app must go through the verification process to remove that warning and other limitations. During the development phase, you can continue past this warning by selecting Advanced > Go to {Project Name} (unsafe).

File not found error for credentials.json

When running the sample, you might receive a file not found or no such file error regarding credentials.json.

This error occurs when you have not authorized the desktop application credentials as detailed in the Prerequisites section above. To learn how to create credentials for a desktop application, go to Create credentials.

Once you create the credentials, make sure the downloaded JSON file is saved as credentials.json. Then move the file to your working directory with the rest of the sample quickstart code.

Further reading