Programmable SMS Quickstart for C# with .NET Core
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.
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.
One of the easiest ways to install the CLI on Mac OS X is to use Homebrew. If you don't already have it installed, visit the Homebrew site for installation instructions and then return here.
Once Homebrew is installed, simply run the following command to install the CLI:
brew tap twilio/brew && brew install twilio
Updating
If you already installed the CLI with brew and want to upgrade to the latest version, run:
brew upgrade twilio
Warning for Node.js developers
If you have installed Node.js version 10.12 or higher on your Mac, you can avoid potential Node.js version conflicts by installing the CLI using npm:
npm install twilio-cli -g
Before we can install, we need to make sure you have Node.js installed (version 10.12 or above). To see if you have node installed, try running this command:
node -v
If your system reports v10.12.0 or above, you can skip the next step.
Installing Node.js on Windows
Using the Windows Installer (.msi) is the recommended way to install Node.js on Windows. You can download the installer from the Node.js download page.
Installing Twilio CLI
The CLI is installed with npm (Node Package Manager), which comes with Node.js. To install the CLI run the following command:
npm install twilio-cli -g
Note the -g option is what installs the command globally so you can run it from anywhere in your system.
Updating
If you already installed the CLI with npm and want to upgrade to the latest version, run:
npm install twilio-cli@latest -g
Before we can install, we need to make sure you have Node.js installed (version 10.12 or above). Even if you already installed Node yourself, the CLI works best when you install it using nvm. Here's how to get nvm installed on most Linux systems:
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.34.0/install.sh | bash
Please visit the nvm installation instructions for additional options and troubleshooting steps. Once you have nvm installed, run the following to install and use the most recent LTS release of Node.js:
nvm install --lts nvm use <insert version reported from above>
Installing other Twilio CLI prerequisites for Linux
Depending on your distribution, you will need to run one of the following commands:
- Debian/Ubuntu:
sudo apt-get install libsecret-1-dev
- Red Hat-based:
sudo yum install libsecret-devel
- Arch Linux:
sudo pacman -S libsecret
Installing Twilio CLI
The CLI is installed with npm (Node Package Manager), which comes with Node.js. To install the CLI run the following command:
npm install twilio-cli -g
Note the -g option is what installs the command globally so you can run it from anywhere in your system.
Updating
If you already installed the CLI with npm and want to upgrade to the latest version, run:
npm install twilio-cli@latest -g
Run twilio login
to get the Twilio CLI connected to your account. Visit https://www.twilio.com/console, and you’ll find your unique Account SID and Auth Token to provide to the CLI.
You can reveal your auth token by clicking on the eyeball icon:
Get a phone number
If you don't currently own a Twilio phone number with SMS functionality, you'll need to purchase one. With the CLI, run:
twilio phone-numbers:buy:local --country-code US --sms-enabled
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 --version
You 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 Twilio
Send 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 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
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.Core
Create 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 run your application with:
dotnet run
In your favorite browser, open the URL https://localhost:5001/sms.
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. Just run this CLI command, replacing the phone number with your own Twilio phone number:
twilio phone-numbers:update "+15017122661" --sms-url="https://localhost:5001/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 browsing the Twilio tag on Stack Overflow.