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Programmable Messaging Quickstart for C# with .NET Core


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Ahoy there! All messaging transmitted using Twilio's messaging channels is treated as Application-to-Person (A2P) messaging and subject to Twilio's Messaging Policy(link takes you to an external page). For detailed information on policy rules to ensure you remain compliant while using Twilio's services, please see our Acceptable Use Policy(link takes you to an external page).

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Looking for .NET Framework? We have a quickstart for that too!

With just a few lines of code, your .NET Core application can send and receive text messages with Twilio Programmable SMS.

This C# SMS Quickstart will teach you how to do this using our Communications REST API and the Twilio helper library for .NET Core.

In this Quickstart, you will learn how to:

  1. Sign up for Twilio and get your first SMS-enabled Twilio phone number
  2. Set up your development environment to send and receive messages
  3. Send your first SMS
  4. Receive inbound text messages
  5. Reply to incoming messages with an SMS

Prefer to get started by watching a video? Check out our C# SMS Quickstart video on Youtube(link takes you to an external page).


Sign up for - or sign in to - Twilio

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Already have a Twilio account? Go ahead and skip this section.

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If you are sending SMS to the U.S. or Canada, before proceeding further please be aware of updated restrictions on the use of Toll-Free numbers for messaging, including TF numbers obtained through Free Trial. Please click here(link takes you to an external page) for details.

You can sign up for a free Twilio trial account here(link takes you to an external page).

  • When you sign up, you'll be asked to verify your personal phone number. This helps Twilio verify your identity and also allows you to send test messages to your phone from your Twilio account while in trial mode.
  • Once you verify your number, you'll be asked a series of questions to customize your experience.
  • Once you finish the onboarding flow, you'll arrive at your project dashboard in the Twilio Console(link takes you to an external page) . This is where you'll be able to access your Account SID, authentication token, find a Twilio phone number, and more.

If you don't currently own a Twilio phone number with SMS functionality, you'll need to purchase one. After navigating to the Buy a Number(link takes you to an external page) page, check the SMS box and click Search.

Buy a twilio phone number.

You'll then see a list of available phone numbers and their capabilities. Find a number that suits your fancy and click Buy to add it to your account.

Select an SMS-enabled phone number.

We'll need to use the Twilio CLI (command line interface) for a few tasks, so let's install that next.

macOSWindowsLinux

The suggested way to install twilio-cli on macOS is to use Homebrew(link takes you to an external page). If you don't already have it installed, visit the Homebrew site(link takes you to an external page) for installation instructions and then return here.

Once you have installed Homebrew, run the following command to install twilio-cli:


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brew tap twilio/brew && brew install twilio

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For other installation methods, see the Twilio CLI Quickstart.

Log in to the Twilio CLI

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Run twilio login to get the Twilio CLI connected to your account. Visit the Twilio Console(link takes you to an external page), and under Account Info, you'll find your unique Account SID and Auth Token to provide to the CLI.

Next, we need to install .NET Core and the Twilio C# Helper Library.


You can check if you already have .NET Core installed on your machine by opening up a command prompt or terminal and running the following command:


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dotnet --version

You should see something like 2.1.3. If you receive an error message, you can download .NET Core from Microsoft(link takes you to an external page) and install it.


Create a new project and add the Twilio NuGet package

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Run these commands to create a new .NET project and install the Twilio NuGet package:


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mkdir TwilioSend
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cd TwilioSend
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dotnet new console
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dotnet add package Twilio


Send an outbound SMS message with C#

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Now that we have .NET Core and the Twilio .NET NuGet package installed, we can send an outbound text message from the Twilio phone number we just purchased with a single API request. Open the file in your new project called Program.cs and type or paste in this code sample, replacing the template code that's already there.

Send an SMS Using Twilio with C#

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This code creates a new instance of the Message resource.

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: "Join Earth's mightiest heroes. Like Kevin Bacon.",
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from: new Twilio.Types.PhoneNumber("+15017122661"),
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to: new Twilio.Types.PhoneNumber("+15558675310")
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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": "Join Earth's mightiest heroes. Like Kevin Bacon.",
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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": "+15017122661",
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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": "+15558675310",
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"uri": "/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Messages/SMXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.json"
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}

You'll need to edit this file a little more before your message will send:

Replace the placeholder credential values

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Swap the placeholder values for accountSid and authToken with your personal Twilio credentials. Go to Twilio Console(link takes you to an external page) and log in. On this page, you'll find your unique Account SID and Auth Token, which you'll need any time you send messages through the Twilio Client like this.

Edit Program.cs and replace the values for accountSid and authToken with your unique values.

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Please note: it's okay to hardcode your credentials when getting started, but you should use configuration to keep them secret before deploying to production. We've written blog posts on how to secure user secrets in a .NET Core Web App(link takes you to an external page) and a .NET Core Console App(link takes you to an external page) that should provide you with some good guidance.

Replace the "from" phone number

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Remember that SMS-enabled phone number you bought just a few minutes ago? Go ahead and replace the existing from number with that one, making sure to use E.164 formatting:

[+][country code][phone number including area code]

Replace the "to" phone number

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Replace the to phone number with your mobile phone number. This can be any phone number that can receive text messages, but it's a good idea to test with your own phone, so you can see the magic happen! As above, you should use E.164 formatting for this value.

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Warning

If you are on a Twilio Trial account, your outgoing SMS messages are limited to phone numbers that you have verified with Twilio. Phone numbers can be verified via your Twilio Console's Verified Caller IDs(link takes you to an external page).

Save your changes and run this code:


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dotnet run

That's it! In a few moments, you should receive an SMS from your Twilio number on your phone.

Are your customers in the U.S. or Canada? You can also send them MMS messages by adding just one line of code. Check out this sending MMS tutorial to see how it's done.


Receive and reply to inbound SMS messages with ASP.NET Core

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When your Twilio number receives an incoming message, Twilio will send an HTTP request to a server you control. This callback mechanism is known as a webhook. When Twilio sends your application a request, it expects a response in the TwiML XML format telling it how to respond to the message. Let's see how we would build this in C# using ASP.NET Core.

Create a new ASP.NET Core project

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Run these commands to create a new ASP.NET Core project and install the Twilio NuGet package:


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mkdir TwilioReceive
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cd TwilioReceive
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dotnet new mvc
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dotnet add package Twilio.AspNet.Core

In the directory named Controllers, create a new Controller called SmsController.cs and use the following code to create a server that can handle incoming messages.

Respond to an incoming text message

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When your phone number receives an incoming message, Twilio will send an HTTP request to your server. This code shows how your server should respond to reply with a text message (using TwiML).


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// Code sample for ASP.NET Core on .NET Core
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// From command prompt, run:
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// dotnet add package Twilio.AspNet.Core
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using Twilio.AspNet.Common;
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using Twilio.AspNet.Core;
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using Twilio.TwiML;
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namespace TwilioReceive.Controllers
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{
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public class SmsController : TwilioController
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{
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public TwiMLResult Index(SmsRequest incomingMessage)
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{
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var messagingResponse = new MessagingResponse();
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messagingResponse.Message("The copy cat says: " +
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incomingMessage.Body);
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return TwiML(messagingResponse);
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}
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}
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}

Save the file, then return to the root folder in your project and run your application with:


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dotnet run

In your favorite browser, open the URL http://localhost:5242/sms(link takes you to an external page) (the port may be different on your computer; check the output of the previous command to identify your port).

If all went well, you should see XML in your browser with the message we'd like to reply with to all our inbound texts. And, yes, that's all the code you need - there's just one more step before everything is wired up.

Configure ngrok and your webhook URL

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We'll use ngrok to set up a tunnel from the public internet to your localhost. This will let us use a public URL as the webhook for your application.

First, download and configure ngrok(link takes you to an external page).

Next, run this command to have ngrok set up a tunnel to your localhost:


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ngrok http 5242

This will start an ngrok tunnel. Copy down the Forwarding URL that ends with ngrok.io.

Then, you need to configure your Twilio phone number to call your webhook URL whenever a new message comes in:

  1. Go to Phone Numbers > Active Numbers in the Twilio Console(link takes you to an external page) .
  2. Select the SMS-enabled Twilio number you want to use.
  3. For the A MESSAGE COMES IN webhook, enter the ngrok URL you copied down earlier. Append /sms to the end of the URL.

Test your application with a text

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Make sure your project is running and your ngrok tunnel is running.

With both of those servers running, we're ready for the fun part - testing our new ASP.NET Core SMS application!

Send an SMS from your mobile phone to your Twilio phone number that's configured with this webhook. Your ASP.NET Core app will process the text message, and you'll get your response back as an SMS.


Now that you know the basics of sending and receiving SMS and MMS text messages with C# and .NET, you might want to check out these resources.

Happy hacking!


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