Programmable Messaging for WhatsApp and C#/.NET Quickstart

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.

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Sign up for Twilio and activate the Sandbox

Before you can send a WhatsApp message from your web language, you'll need to sign up for a Twilio account or sign into your existing account and activate the Twilio Sandbox for WhatsApp. 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.

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>.

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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class Program

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{

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static void Main(string[] args)

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{

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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 = MessageResource.Create(

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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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);

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Console.WriteLine(message.Sid);

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}

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}

Output

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{

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"account_sid": "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",

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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": "MGXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",

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"sid": "SMXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",

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"status": "queued",

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"subresource_uris": {

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"media": "/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Messages/SMXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Media.json"

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},

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"to": "whatsapp:+15005550006",

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"uri": "/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Messages/SMXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.json"

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}

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Receive and reply to messages from WhatsApp

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.

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