.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:

  • Visual Studio 2013 or later
  • A Google account with Google Tasks enabled

Step 1: Turn on the Google Tasks API

Click this button to create a new Cloud Platform project and automatically enable the Google Tasks API:

Enable the Google Tasks API

In resulting dialog click DOWNLOAD CLIENT CONFIGURATION and save the file credentials.json to your working directory.

Step 2: 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 3: Set up the sample

  1. Drag credentials.json (downloaded in Step 1) 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.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace TasksQuickstart
{
    class Program
    {
        // If modifying these scopes, delete your previously saved credentials
        // at ~/.credentials/tasks-dotnet-quickstart.json
        static string[] Scopes = { TasksService.Scope.TasksReadonly };
        static string ApplicationName = "Google Tasks API .NET Quickstart";

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

            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.Load(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)
            {
                foreach (var taskList in taskLists)
                {
                    Console.WriteLine("{0} ({1})", taskList.Title, taskList.Id);
                }
            }
            else
            {
                Console.WriteLine("No task lists found.");
            }
            Console.Read();

        }
    }
}

Step 4: Run the sample

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

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

  1. The sample will attempt 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 are not already logged into your Google account, you will be prompted to log in. If you are logged into multiple Google accounts, you will be asked to select one account to use for the authorization.

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

Notes

  • Authorization information is stored on the file system, so subsequent executions will not 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.

Further reading

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 will be prompted to restart Visual Studio to complete the installation.

This app isn't verified.

The OAuth consent screen that is presented to the user may show the warning "This app isn't verified" if it is requesting scopes that provide access to sensitive user data. These applications must eventually go through the verification process to remove that warning and other limitations. During the development phase you can continue past this warning by clicking Advanced > Go to {Project Name} (unsafe).