Programmable Messaging Quickstart for C# with .NET Core
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. For detailed information on policy rules to ensure you remain compliant while using Twilio’s services, please see our Acceptable Use Policy.
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:
- Sign up for Twilio and get your first SMS-enabled Twilio phone number
- Set up your development environment to send and receive messages
- Send your first SMS
- Receive inbound text messages
- Reply to incoming messages with an SMS
Prefer to get started by watching a video? Check out our C# SMS Quickstart video on Youtube.
Sign up for - or sign in to - Twilio
Already have a Twilio account? Go ahead and skip this section.
You can sign up for a free Twilio trial account here.
- 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. This is where you'll be able to access your Account SID, authentication token, find a Twilio phone number, and more.
Install the Twilio CLI
We'll need to use the Twilio CLI (command line interface) for a few tasks, so let's install that next.
The suggested way to install twilio-cli on macOS is to use Homebrew. If you don’t already have it installed, visit the Homebrew site for installation instructions and then return here.
Once you have installed Homebrew, run the following command to install twilio-cli:
brew tap twilio/brew && brew install twilioThe suggested way to install twilio-cli is by using Scoop, a command-line installer for Windows. If you don’t already have it installed, visit the Scoop site for installation instructions and then return here.
Note PowerShell will need to be run as an administrator to avoid common permission issues when installing via Scoop.
- Add the
twilio-cliBucket:
scoop bucket add twilio-scoop https://github.com/twilio/scoop-twilio-cli - Install the app:
scoop install twilio
twilio-cli can be installed using the Advanced Package Tool (apt) on most distributions such as Debian, Ubuntu, and Mint.
To do so, run the following commands in your terminal:
wget -qO- https://twilio-cli-prod.s3.amazonaws.com/twilio_pub.asc \
| sudo apt-key add -
sudo touch /etc/apt/sources.list.d/twilio.list
echo 'deb https://twilio-cli-prod.s3.amazonaws.com/apt/ /' \
| sudo tee /etc/apt/sources.list.d/twilio.list
sudo apt update
sudo apt install -y twilioFor other installation methods, see the Twilio CLI Quickstart.
Run twilio login to get the Twilio CLI connected to your account. Visit the Twilio console, and you’ll find your unique Account SID and Auth Token to provide to the CLI.
Get a phone number
If you don't currently own a Twilio phone number with SMS functionality, you'll need to purchase one. You can either use the Twilio CLI to do this or obtain one through the Twilio console.
With the CLI, run:
twilio phone-numbers:buy:local --country-code US --sms-enabledTo obtain a number through the Twilio console, go to Phone Numbers > Manage > Buy a Number.
Replace US with your ISO-3166-1 country code if you would like a phone number in another country. If you aren't finding any SMS enabled numbers, try looking for a mobile number instead of a local number: twilio phone-numbers:buy:mobile --country-code DE --sms-enabled
Select a phone number to add it to your account.
Next, we need to install .NET Core and the Twilio C# Helper Library.
Install .NET Core
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:
dotnet --versionYou should see something like 2.1.3. If you receive an error message, you can download .NET Core from Microsoft and install it.
Create a new project and add the Twilio NuGet package
Run these commands to create a new .NET project and install the Twilio NuGet package:
mkdir TwilioSend
cd TwilioSend
dotnet new console
dotnet add package TwilioSend an outbound SMS message with C#
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.
You’ll need to edit this file a little more before your message will send:
Replace the placeholder credential values
Swap the placeholder values for accountSid and authToken with your personal Twilio credentials. Go to https://www.twilio.com/console 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. You can reveal your auth token by clicking on the 'view' link:
Edit Program.cs and replace the values for accountSid and authToken with your unique values.
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 and a .NET Core Console App that should provide you with some good guidance.
Replace the "from" phone number
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
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.
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.
Save your changes and run this code:
dotnet runThat'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
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
Run these commands to create a new ASP.NET Core project and install the Twilio NuGet package:
mkdir TwilioReceive
cd TwilioReceive
dotnet new mvc
dotnet add package Twilio.AspNet.CoreCreate a new controller
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.
Save the file, then return to the root folder in your project and run your application with:
dotnet runIn your favorite browser, open the URL http://localhost:5242/sms (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 your Webhook URL
Now, you need to configure your Twilio phone number to call your webhook URL whenever a new message comes in. In a new terminal window, run this command, replacing the phone number with your own Twilio phone number and 5242 with the port your application is using:
twilio phone-numbers:update "+15017122661" --sms-url="http://localhost:5242/sms"The CLI will start an ngrok tunnel (so Twilio can reach your development machine) and wait patiently for incoming text messages!
Test your application with a text
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.
Where to next?
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.
- REST API documentation
- TwiML reference docs
- Tutorials with full sample applications in C#
- Secure your C# / ASP.NET app by validating incoming Twilio requests
Happy hacking!
Need some help?
We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd by visiting Twilio's Stack Overflow Collective or browsing the Twilio tag on Stack Overflow.
