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This document provides all the basic information you need to start using the library.
It covers the library concepts,
shows examples for various use cases,
and gives links to more information.
Setup
There are a few setup steps you need to complete before you can use this library:
If you don't already have a Google account,
sign up.
It is important to understand the basics of how API authentication and authorization are handled.
All API calls must use either simple or authorized access (defined below).
Many API methods require authorized access, but some can use either.
Some API methods that can use either behave differently,
depending on whether you use simple or authorized access.
See the API's method documentation to determine the appropriate access type.
1. Simple API access (API keys)
These API calls do not access any private user data.
Your application must authenticate itself as an application belonging
to your Google API Console project.
This is needed to measure project usage for accounting purposes.
API key:
To authenticate your application, use an
API key
for your API Console project.
Every simple access call your application makes must include this key.
2. Authorized API access (OAuth 2.0)
These API calls access private user data.
Before you can call them,
the user that has access to the private data must grant your application access.
Therefore, your application must be authenticated,
the user must grant access for your application,
and the user must be authenticated in order to grant that access.
All of this is accomplished with
OAuth 2.0 and libraries written for it.
Scope:
Each API defines one or more scopes that declare a set of operations permitted.
For example, an API might have read-only and read-write scopes.
When your application requests access to user data,
the request must include one or more scopes.
The user needs to approve the scope of access your application is requesting.
Refresh and access tokens:
When a user grants your application access, the OAuth 2.0 authorization server
provides your application with refresh and access tokens.
These tokens are only valid for the scope requested.
Your application uses access tokens to authorize API calls.
Access tokens expire, but refresh tokens do not.
Your application can use a refresh token to acquire a new access token.
Client ID and client secret:
These strings uniquely identify your application and are used to acquire tokens.
They are created for your project on the API Console.
There are three types of client IDs,
so be sure to get the correct type for your application:
In this section, there are examples of simple API usage without authorization.
For more information about authorization calls, see the
OAuth 2.0 page for .NET.
Simple API example
This example uses simple API access for a command-line application.
It calls the
Google Discovery API to list all Google APIs.
Setup for example
Get your Simple API key. To find your application's API key, do the following:
This API supports two types of credentials.
Create whichever credentials are appropriate for your project:
OAuth 2.0: Whenever your application requests private user
data, it must send an OAuth 2.0 token along with the request. Your
application first sends a client ID and, possibly, a client secret to
obtain a token. You can generate OAuth 2.0 credentials for web
applications, service accounts, or installed applications.
API keys:
A request that does not provide an OAuth 2.0 token must send an API
key.
The key identifies your project and provides API access, quota, and
reports.
The API supports several types of restrictions on API keys. If the API key that you
need doesn't already exist, then create an API key in the Console by
clicking Create credentials
> API key. You can restrict the key before using it
in production by clicking Restrict key and selecting one of the
Restrictions.
usingSystem;usingSystem.Threading.Tasks;usingGoogle.Apis.Discovery.v1;usingGoogle.Apis.Discovery.v1.Data;usingGoogle.Apis.Services;namespaceDiscovery.ListAPIs{///<summary>
///ThisexampleusesthediscoveryAPItolistallAPIsinthediscoveryrepository.///https://developers.google.com/discovery/v1/using.///<summary>
classProgram{[STAThread]staticvoidMain(string[]args){Console.WriteLine("Discovery API Sample");Console.WriteLine("====================");try{newProgram().Run().Wait();}catch(AggregateExceptionex){foreach(vareinex.InnerExceptions){Console.WriteLine("ERROR: "+e.Message);}}Console.WriteLine("Press any key to continue...");Console.ReadKey();}privateasyncTaskRun(){//Createtheservice.varservice=newDiscoveryService(newBaseClientService.Initializer{ApplicationName="Discovery Sample",ApiKey="[YOUR_API_KEY_HERE]",});//Runtherequest.Console.WriteLine("Executing a list request...");varresult=awaitservice.Apis.List().ExecuteAsync();//Displaytheresults.if(result.Items!=null){foreach(DirectoryList.ItemsDataapiinresult.Items){Console.WriteLine(api.Id+" - "+api.Title);}}}}}
Tips for using API keys:
In order to use a specific service, you have to add a reference to it.
For example if you want to use the
Tasks API,
you should install its NuGet package
Google.Apis.Tasks.v1.
To create an instance of a service, just call its constructor. For example:
new TasksService(new BaseClientService.Initializer {...});".
All methods of a service are located on individual resources on the service object itself.
The Discovery service has an Apis resource, which contains a List method.
When you call service.Apis.List(..) a request object targeting this method is returned.
To execute a request, call the Execute() or ExecuteAsyc() method on a request.
Set the API key using the ApiKey property on the BaseClientService.Initializer instance.
Finding information about the APIs
The
Supported APIs
page lists all APIs that can be accessed using this library as well as links to documentation.
You can also use the
APIs Explorer
to browse APIs, list available methods, and even try API calls from your browser.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-05-07 UTC."],[[["\u003cp\u003eThis documentation provides an overview of using the Google API client library for .NET, including setup, authentication, and usage examples.\u003c/p\u003e\n"],["\u003cp\u003eBefore using the library, ensure you have a Google account, a Google API Console project, and install the necessary NuGet package.\u003c/p\u003e\n"],["\u003cp\u003eThe library supports both simple API access using API keys and authorized access with OAuth 2.0 for private user data.\u003c/p\u003e\n"],["\u003cp\u003eSimple API access requires an API key for project usage tracking, while authorized access necessitates OAuth 2.0 for user data access.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for basic API usage and guidance on locating further information about supported APIs and the APIs Explorer is included.\u003c/p\u003e\n"]]],[],null,["This document provides all the basic information you need to start using the library.\nIt covers the library concepts,\nshows examples for various use cases,\nand gives links to more information.\n\nSetup\n\n\nThere are a few setup steps you need to complete before you can use this library:\n\n1. If you don't already have a Google account, [sign up](https://www.google.com/accounts).\n2. If you have never created a Google API Console project, read the [Managing Projects page](/console/help/managing-projects) and create a project in the [Google API Console](https://console.cloud.google.com/).\n3. [Install](http://www.nuget.org/packages?q=google.apis&prerelease=true&sortOrder=relevance) the NuGet package you want to work with.\n\nAuthentication and authorization\n\n\nIt is important to understand the basics of how API authentication and authorization are handled.\nAll API calls must use either simple or authorized access (defined below).\nMany API methods require authorized access, but some can use either.\nSome API methods that can use either behave differently,\ndepending on whether you use simple or authorized access.\nSee the API's method documentation to determine the appropriate access type.\n\n1. Simple API access (API keys)\n\n\nThese API calls do not access any private user data.\nYour application must authenticate itself as an application belonging\nto your Google API Console project.\nThis is needed to measure project usage for accounting purposes.\n\n\n**API key** :\nTo authenticate your application, use an\n[API key](/console/help/using-keys)\nfor your API Console project.\nEvery simple access call your application makes must include this key.\n| **Warning**: Keep your API key private. If someone obtains your key, they could use it to consume your quota or incur charges against your API Console project.\n\n\u003cbr /\u003e\n\n2. Authorized API access (OAuth 2.0)\n\n\nThese API calls access private user data.\nBefore you can call them,\nthe user that has access to the private data must grant your application access.\nTherefore, your application must be authenticated,\nthe user must grant access for your application,\nand the user must be authenticated in order to grant that access.\nAll of this is accomplished with\n[OAuth 2.0](/accounts/docs/OAuth2) and libraries written for it.\n\n\n**Scope**:\nEach API defines one or more scopes that declare a set of operations permitted.\nFor example, an API might have read-only and read-write scopes.\nWhen your application requests access to user data,\nthe request must include one or more scopes.\nThe user needs to approve the scope of access your application is requesting.\n\n\n**Refresh and access tokens**:\nWhen a user grants your application access, the OAuth 2.0 authorization server\nprovides your application with refresh and access tokens.\nThese tokens are only valid for the scope requested.\nYour application uses access tokens to authorize API calls.\nAccess tokens expire, but refresh tokens do not.\nYour application can use a refresh token to acquire a new access token.\n| **Warning**: Keep refresh and access tokens private. If someone obtains your tokens, they could use them to access private user data.\n\n\u003cbr /\u003e\n\n\n**Client ID and client secret** :\nThese strings uniquely identify your application and are used to acquire tokens.\nThey are created for your project on the [API Console](https://console.cloud.google.com/).\nThere are three types of client IDs,\nso be sure to get the correct type for your application:\n\n- [Web application](/accounts/docs/OAuth2WebServer) client IDs\n- [Installed application](/accounts/docs/OAuth2InstalledApp) client IDs\n- [Service Account](/accounts/docs/OAuth2ServiceAccount) client IDs\n\n| **Warning**: Keep your client secret private. If someone obtains your client secret, they could use it to consume your quota, incur charges against your Console project, and request access to user data.\n\n\u003cbr /\u003e\n\nExamples\n\n\nIn this section, there are examples of simple API usage without authorization.\nFor more information about authorization calls, see the\n[OAuth 2.0 page for .NET](/api-client-library/dotnet/guide/aaa_oauth).\n\nSimple API example\n\n\nThis example uses simple API access for a command-line application.\nIt calls the\n[Google Discovery API](/discovery) to list all Google APIs.\n\nSetup for example\n\n\n**Get your Simple API key**. To find your application's API key, do the following:\n\n\n1. Open the [Credentials page](https://console.cloud.google.com/apis/credentials) in the API Console.\n2. This API supports two types of credentials. Create whichever credentials are appropriate for your project:\n - **OAuth 2.0:** Whenever your application requests private user\n data, it must send an OAuth 2.0 token along with the request. Your\n application first sends a client ID and, possibly, a client secret to\n obtain a token. You can generate OAuth 2.0 credentials for web\n applications, service accounts, or installed applications.\n\n For more information, see the [OAuth 2.0 documentation](https://developers.google.com/identity/protocols/OAuth2).\n - **API keys:**\n\n A request that does not provide an OAuth 2.0 token must send an API\n key.\n\n The key identifies your project and provides API access, quota, and\n reports.\n\n The API supports several types of restrictions on API keys. If the API key that you\n need doesn't already exist, then create an API key in the Console by\n clicking **[Create credentials](https://console.cloud.google.com/apis/credentials) \\\u003e API key** . You can restrict the key before using it\n in production by clicking **Restrict key** and selecting one of the\n **Restrictions**.\n\nTo keep your API keys secure, follow the [best practices for\nsecurely using API keys](//cloud.google.com/docs/authentication/api-keys).\n\n\u003cbr /\u003e\n\nCode for example \n\n```transact-sql\nusing System;\nusing System.Threading.Tasks;\n\nusing Google.Apis.Discovery.v1;\nusing Google.Apis.Discovery.v1.Data;\nusing Google.Apis.Services;\n\nnamespace Discovery.ListAPIs\n{\n /// \u003csummary\u003e\n /// This example uses the discovery API to list all APIs in the discovery repository.\n /// https://developers.google.com/discovery/v1/using.\n /// \u003csummary\u003e\n class Program\n {\n [STAThread]\n static void Main(string[] args)\n {\n Console.WriteLine(\"Discovery API Sample\");\n Console.WriteLine(\"====================\");\n try\n {\n new Program().Run().Wait();\n }\n catch (AggregateException ex)\n {\n foreach (var e in ex.InnerExceptions)\n {\n Console.WriteLine(\"ERROR: \" + e.Message);\n }\n }\n Console.WriteLine(\"Press any key to continue...\");\n Console.ReadKey();\n }\n\n private async Task Run()\n {\n // Create the service.\n var service = new DiscoveryService(new BaseClientService.Initializer\n {\n ApplicationName = \"Discovery Sample\",\n ApiKey=\"[YOUR_API_KEY_HERE]\",\n });\n\n // Run the request.\n Console.WriteLine(\"Executing a list request...\");\n var result = await service.Apis.List().ExecuteAsync();\n\n // Display the results.\n if (result.Items != null)\n {\n foreach (DirectoryList.ItemsData api in result.Items)\n {\n Console.WriteLine(api.Id + \" - \" + api.Title);\n }\n }\n }\n }\n}\n```\n\n\nTips for using API keys:\n\n- In order to use a specific service, you have to add a reference to it. For example if you want to use the [Tasks API](https://developers.google.com/google-apps/tasks/), you should install its NuGet package [Google.Apis.Tasks.v1](http://www.nuget.org/packages/Google.Apis.Tasks.v1/).\n- To create an instance of a service, just call its constructor. For example: `new TasksService(new BaseClientService.Initializer {...});\"`.\n- All methods of a service are located on individual resources on the service object itself. The Discovery service has an `Apis` resource, which contains a `List` method. When you call `service.Apis.List(..)` a request object targeting this method is returned. \n To execute a request, call the `Execute()` or `ExecuteAsyc()` method on a request.\n- Set the API key using the `ApiKey` property on the `BaseClientService.Initializer` instance.\n\nFinding information about the APIs\n\n\nThe\n[Supported APIs](/api-client-library/dotnet/apis)\npage lists all APIs that can be accessed using this library as well as links to documentation.\n\n\nYou can also use the\n[APIs Explorer](/apis-explorer)\nto browse APIs, list available methods, and even try API calls from your browser."]]