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Programmable Messaging for WhatsApp and C#/.NET Quickstart


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Warning

Twilio is launching a new Console. Some screenshots on this page may show the Legacy Console and therefore may no longer be accurate. We are working to update all screenshots to reflect the new Console experience. Learn more about the new Console(link takes you to an external page).

With just a few lines of code, your application can send and receive messages with WhatsApp using the Twilio API for WhatsApp.

This WhatsApp Quickstart will teach you how to do this using the Twilio Sandbox for WhatsApp, C#/.NET, and the Twilio .NET Twilio helper library. In this Quickstart, you will learn how to:

  1. Sign up for Twilio and activate the Sandbox.
  2. Set up your development environment to send and receive messages
  3. Opt-in to the Sandbox
  4. Send your first WhatsApp message
  5. Receive inbound WhatsApp messages
  6. Reply to incoming WhatsApp messages

Prefer to watch a video? The video below shows you how to use the Sandbox to send and receive WhatsApp messages.


Sign up for Twilio and activate the Sandbox

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Before you can send a WhatsApp message from your web language, you'll need to sign up for a Twilio account(link takes you to an external page) or sign into your existing account and activate the Twilio Sandbox for WhatsApp(link takes you to an external page). It allows you to prototype with WhatsApp immediately using a shared phone number, without waiting for a dedicated number to be approved by WhatsApp.

To get started, select a number from the available sandbox numbers to activate your sandbox.

WA_Sandbox.

Be sure to take note of the phone number you choose in the Sandbox. You will need this later when we're ready to send some messages.


Gather your Twilio account information

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Before you can send any messages, you'll need to gather your Twilio account credentials. You can find these in the Twilio Console(link takes you to an external page).

  • Account SID - Used to authenticate REST API requests
  • Auth Token - Used to authenticate REST API requests
Account Credentials.

For all of our code snippets and curl examples, you will need to authenticate with the Account SID and Auth Token.


Set up your C# development environment

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The next steps will involve writing some code. We've written up development environment setup for C#/.NET, where you'll set up a dev environment and prepare to build a simple web app.

If you haven't yet set up your development environment to write some C#, head there first to get ready. This quickstart will be waiting.


Send a message with WhatsApp in C#

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Opt-in required for WhatsApp Sandbox numbers

The WhatsApp Sandbox uses a single WhatsApp Sender shared by all Twilio users. To begin using the WhatsApp Sandbox, you must send a join message from the number you wish to send outbound messages. Each number may only recieve messages from one WhatsApp Sandbox at a time.

When registering your own WhatsApp Sender, these limits do not apply. Learn how to register your own WhatsApp Senders.

Sandbox Opt-in Message

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Send "join <your sandbox keyword>" to your Sandbox number in WhatsApp to join your Sandbox, and we'll reply with a confirmation that you've joined. Your sandbox keyword can be found in the console.

Once you join, you will only receive messages from your specific Sandbox. To disconnect from the sandbox, you can reply to the message from WhatsApp with sandbox stop, or switch to a different sandbox by messaging join <other sandbox keyword>.

Screen Shot 2018-08-01 at 8.31.05 AM.

Inviting other users to your sandbox (OPTIONAL)

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To invite someone else to your sandbox, create a link with the following format containing the opt-in message and send it to them: whatsapp://send?phone=<Your Sandbox Number>&text=<your URL-encoded sandbox keyword>

You can also create a QR code(link takes you to an external page) with the link format above that users can scan on their phone to opt-in to your sandbox.

whatsapp-sandbox-opt-in-qr.

To send a message, use the following code and replace the to parameter with the phone number for your personal WhatsApp account in the E.164 format. (If you haven't already, install WhatsApp on your device and register for an account.) For the from parameter, be sure to include the whatsapp: channel identifier before the Sandbox number in E.164 format.

For the From parameter, you need your Sender ID which should be shown on the installed channel in the Twilio Console, as shown previously.

Send a message with WhatsApp and C#

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C#

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// Install the C# / .NET helper library from twilio.com/docs/csharp/install
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using System;
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using Twilio;
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using Twilio.Rest.Api.V2010.Account;
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using System.Threading.Tasks;
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class Program {
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public static async Task Main(string[] args) {
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// Find your Account SID and Auth Token at twilio.com/console
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// and set the environment variables. See http://twil.io/secure
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string accountSid = Environment.GetEnvironmentVariable("TWILIO_ACCOUNT_SID");
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string authToken = Environment.GetEnvironmentVariable("TWILIO_AUTH_TOKEN");
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TwilioClient.Init(accountSid, authToken);
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var message = await MessageResource.CreateAsync(
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body: "Hello there!",
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from: new Twilio.Types.PhoneNumber("whatsapp:+14155238886"),
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to: new Twilio.Types.PhoneNumber("whatsapp:+15005550006"));
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Console.WriteLine(message.Body);
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}
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}

Output

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{
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"account_sid": "ACaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
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"api_version": "2010-04-01",
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"body": "Hello there!",
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"date_created": "Thu, 24 Aug 2023 05:01:45 +0000",
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"date_sent": "Thu, 24 Aug 2023 05:01:45 +0000",
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"date_updated": "Thu, 24 Aug 2023 05:01:45 +0000",
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"direction": "outbound-api",
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"error_code": null,
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"error_message": null,
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"from": "whatsapp:+14155238886",
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"num_media": "0",
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"num_segments": "1",
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"price": null,
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"price_unit": null,
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"messaging_service_sid": "MGaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
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"sid": "SMaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
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"status": "queued",
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"subresource_uris": {
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"media": "/2010-04-01/Accounts/ACaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/Messages/SMaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/Media.json"
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},
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"tags": {
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"campaign_name": "Spring Sale 2022",
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"message_type": "cart_abandoned"
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},
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"to": "whatsapp:+15005550006",
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"uri": "/2010-04-01/Accounts/ACaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/Messages/SMaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.json"
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}


Receive and reply to messages from WhatsApp

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When someone replies to one of your messages, you will receive a webhook request from Twilio.

You can configure webhooks by connecting your Sandbox to an app you've already built for handling incoming messages, or build a new one for WhatsApp messages.

Configure WhatsApp Sandbox Webhook.

This webhook request also supports TwiML (the Twilio Markup Language) just like a regular Twilio SMS request.

To handle this request, you need to set up a web application and expose it to the internet. The C#/.NET Programmable Messaging Quickstart shows you how to respond to a message and generate TwiML in C#.

And - that's all there is to it; receiving and responding is exactly the same as you would do in any SMS app with our Messaging API. Cool, right?

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Info

Although these Quickstarts show you how to receive an SMS message, the webhook that Twilio will send will include the same parameters as an incoming SMS message, with the exception that To and From addresses will be set to the WhatsApp number receiving the message (whatsapp:<E.164 formatted Twilio phone number associated with your business>) and the WhatsApp number sending the message (whatsapp:<User's E.164 phone number>), respectively.


What's next for WhatsApp and C#/.NET?

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Because the Twilio WhatsApp API is essentially the same as the Twilio Programmable Messaging API, all of the documentation for that API applies to your apps sending and receiving messages with WhatsApp. To dive deeper with a WhatsApp integration, see the WhatsApp documentation overview as well as the API Reference.

Here are some areas you might like to explore next.

We can't wait to see what kind of WhatsApp integration you build!


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